Digit

(Why) does it have to be 24k? That's pure gold and like Jonas mentioned, gold is soft and will abrade quickly. I'd go for lower-gold-content plating if possible; that's alloyed with copper and will probably better withstand actual use (but might still tarnish in the long run; there's a reason gold items and jewelery need cleaning and polishing once in a while). Electroplating gold directly onto copper or brass risks the copper to come through and tarnish. This can be prevented by nickel-plating first. I'm not sure if you can gold-plate directly onto stainless steel or if you'd need intermediate layers for the gold to deposit on (I know that chrome-plating steel needs a base layer of copper, for example; and silver-plating is also usually done on a copper base iirc).

Looks better than before :-) I think you shifted the top two card pockets a hole too far down though. And next time I'd finish the top edges of those card pockets too ;-)

That's probably why they sell it online; because they have been passed on by people in the store. Online orders are harder for a customer to reject. I only buy in Europe and mostly chrome-tan at that, so my sources wouldn't be helpful. I usually try a first (small) order and I try to order samples too if they have them. So far I've mostly bought large cuts (sides), so there's usually sufficient good quality surface to make what I want.

A tannery takes full hides and produces full hides. When selling leather, intermediaries (or possibly the tannery themselves) cut those hides into manageable parts for different audiences. Upholsterers typically need large surfaces and buy whole hides. They use as much as they can and maybe try to sell off the waste (sometimes very irregular cuts) as scrap for a price per weight unit. I have an upholsterer nearby and they sell small scraps per bag, medium scraps per kilo and larger pieces per sqm. A business making only high-end bags, purses and other small items might pay a premium for a (double) back or (double) butt, which can be cheaper than buying a full hide or side and having to scrap necks and bellies. Made-to-order businesses receiving a request for an item in a fancy (drum-dyed) color might do the same by buying a specific cut that matches the surface of their project; again to limit waste. Resellers on the other hand will differentiate their prices according to what they can sell. They buy whole hides and need to recoup those costs plus earn their living. Selling a whole hide is the easiest and cheapest option for them. If they sell a side, they'll charge a premium because they are left with a side in their stock (which still contains a good quality half-back). If they need to make a more specific cut, such as cutting out the best bits (back/butt, double back/butt), they are left with more lower quality bits in their stock for which there is likely a smaller customer base; so they charge a larger premium for being left with hard-to-sell parts. If I were a reseller I'd probably make sure that a double back cut of a hide at least covers the cost of the full hide.

That's basically what I meant with Except for the skiving bit :-) Exactly my thoughts about tooling, carving, hand-dying and painting leather I just use pre-dyed chrome-tan without adornments, but with some effort put in for finishing edges. Everybody has their own preferences for aesthetics and how much time and effort they'd want to invest.

I'd skive and roll the edge (at least on the 'outside' of the panels), but using contact adhesive. Basting tape will be a pain to stitch through (and also to stick down in curves) and can damage your thread. Notching would depend on the radius and thickness of the (skived) leather; do a test on a bit of scrap first. You can also go for slightly rougher look by skiving the edges of the leather tape really thin and leaving them as-as. And finally you could go for a 'coupé net' where you don't add any leather tape on the edges of the bag panels and seal them with edge paint.

Probably a card stopper to prevent cards from being pushed all the way down to the bottom stitch.

I use lots of water-based contact adhesive on leather and double-sided tape only when I need to combine textile and leather (eg zippers). I use double-sided tape because glue would wick through the textile and become visible. Note that tape adds more thickness than glue and glue is easier than tape to manoeuver around curved edges. Both glue and leather for me are tools to keep stuff together for stitching. I'd never use glue alone for keeping things together. While a properly applied good adhesive should never come loose, that only applies to the few fibers of leather it contacts, the rest of the thickness of the leather can still rip through depending on the foce applied. The thread of a stich goes all the way through the leather and keeps the layers together accross the entire thickness.

Check out https://www.pethardware.com/en/belt-buckles/?pl50=2 and https://www.pethardware.com/en/roller-buckles/?pl50=2 They have a choice of stainless, brass and zinc die-cast.

Best use a roller buckle as those are easier to tighten and something that has some strength (chrome or nickle-plated steel or stainless; zinc die-cast may be ok, but check breaking load in the spec). Otherwise go for what you like best. Roller buckles are available in all kinds of finishes and widths. Lockable buckles exist too, but those are usually limited in width. Note that for lockable buckles you need an oblong punch for the holes instead of a round one and you can't use eyelets.

Pet Hardware in Europe has a large catalog of buckles, snaps, rivets, etc. All in different finishes and wholesale ordering quantities. https://www.pethardware.com/en/

Frequency equals speed of light divided by wavelength: https://en.wikipedia.org/wiki/Frequency#In_wave_propagation Conversely, wavelength equals speed of light divided by frequency. Taking a car key fob with a frequency of 315MHz as an example: wavelength = 299792458 m/s divided by 315000000 Hz = 951.7 mm --> the holes in your faraday cage (mesh) need to be significantly smaller than 951 mm to block this frequency. Taking the other end of the spectrum at mm-wave RFID (24.125 GHz): 299792458 m/s divided by 24125000000 Hz = 12.4mm --> mesh holes need to be significantly smaller than 12 mm to block this frequency. In practice, any fine mesh or solid conducting foil will block (or rather: attenuate) all relevant frequencies.

My German supplier sells narrow belt leather (8mm up to 20mm) in lengths of 50m up to 160m depending on the width. This can be obtained from a hide by circular cutting. The downside is that the further you get to the center of the hide, the more the belt twists. The thinner the leather, the less noticeable the twist I guess and for piping I suppose it matters even less. https://www.lederhuis.com/leather_straps/endless_lace_harness_leather.php I don't know where you're from, but you could try searching for similar stuff in your area and skive it down to the thickness you want, or try to find a supplier with a strap/belt cutting machine that can and is willing to circular-cut a hide of nappa for you.

I think a bag like that (if made from relatively supple leather) would have some sort of reinforcement in the front and rear panels between the outside leather and the inside lining. With age that reinforcement may have sagged or cracked. If support of those panels was indeed achieved via reinforcement rather than the stiffness of the leather itself, trying to re-stiffen the leather won't help. I think you should first try to find out how the bag was constructed (ie does it have reinforcement, possibly sandwiched between layers of leather and lining?) before thinking of how to resolve the problem. If there is indeed reinforcement inside I think you'll have to undo the bottom stitching all accross the horizontal, glue in a strip of new reinforcement (the width of the strip would depend on the amount of sag in the panels), restitch and re-finish the edges. This strip will be visible from the inside of the bag though.

When I started my leatherworking course at school, they offered a small kit containing a snap-off knife, silver pen, a sharp needle, an awl, a glue brush and a glue spatula. Except for the brush, these are all things I use very often (for gluing larger surfaces I use an old credit card for a spatula). To this set I added stuff on an as-needed basis: lighter, steel ruler, cutting mats (I started with an A3 size, but A2 is more convenient), two sizes of saddler's needles (of which I only use one) and a rotary hole punch. There is lots of other stuff you can buy, but you should first have some idea in which direction you're going. I've added some larger equipment pretty fast: a spindle press for setting rivets and an industrial cylinder-arm sewing machine (Adler 69), both second-hand. With all of these tools I now feel confident making small to medium items like wallets, belts, purses, handbags, and clothing. Once you're starting to get the hang of things, the most difficult aspect of leatherwork (imo) is designing things, creating patterns, and getting the idea in your head to a practical execution. When you have a pattern and know in which order all the parts fit together, the rest is just a matter of cutting, glueing and stitching. It helps if you have guidance from an experienced teacher: they can offer practical approaches and solutions that have a track record of use in the industry. Once you know in which direction you're going, you probably want to add other equipment to the base set: If you want to make shoes or boots, you'll likely need more specific sewing machines to stitch hard to reach parts. If you want to make stuff using very thick leather, you probably need a sturdier sewing machine. If you want to tool and/or color leather, you'll need a hammer, punches, a solid base, dyes, etc. The number of tools and machines you can buy for leatherwork is only limited by your budget, but in the end all leatherwork is very similar: you cut up a hide into pieces and then you combine those pieces again into something you can use. So the most basic tools you need are things for cutting leather (a knife) and things for combining leather pieces (needle and thread, glue). For visual appeal, add some stuff to make things beautiful (dyes, paints, tooling, ...).