Sewing next to a lump

[Matt S]

15 hours ago, LePoisson said:

There was also a little pill bottle filled with needles in 2 different lengths. Is there any way to identify what all these needles are (size/tip)?

Size is sometimes laser etched on, but you need keen eyes or magnification to see it. Class is rarely noted on the needle. If you're really keen you can measure it and compare it with manufacturers' drawings to make an educated guess. Tip is simply a visual check, most common are round blunt, round sharp, ball point for knit fabrics, LR/RR slanted cutting for leather etc, straight cutting for leather etc, and a few other odd shapes like triangle cutting. Run the tip down a piece of leather. If it cuts rather than scores or dents the surface it'll probably work to sew leather though it might not give you the look you're after.
 

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Is there anything to beware of with the different lengths if I try using them?

Yes, if you have the wrong class of needle your machine will not work. Too short and your hook won't form a loop, or maybe the needle won't even reach the leather. Too long and you'll get needle strikes, which can damage the machine or send bits of needle in a random direction. If you want to try a needle turn the machine over by hand a few times before switching on the motor!

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Should I just assume that these are old, dull needles and toss them?

Probably. Quality industrial needles of this common sort are £5 per pack of 10. Wrong/worn/damaged/rusted needles can cause a lot more than £5 of damage to your machine, work, person or sanity.