There are a lot of factors that go into the value of this saddle. It's a 1904 style saddle ( there is a later model that had fenders like an english saddle added to a 1904 model--the later style is called the 1928 model) but as to the value of the saddle it's very hard to tell without having the saddle in front of me but there are a few ways to tell if it's more valuable or less.
1 Does the saddle have any date stamps on it? Ussually they are on the quarter straps ( the strap that crosses the pommel and cantle)
2 Do any of the items that are not orriginal to the saddle have date stamps ( the stirrups and stirrup leathers and cinch ring straps and the safes are obviously off a different saddle but how old are they?)
3 What size seat is it?( the seat sizes were 11 11 1/2 and 12 and were marked on the pommel shield)
4 Do you have any more of the coat straps?( that strap that is run through the slot on the pommel is called a coat strap)
5 What does the bottom look like? ( some of these saddles had fleece under the bars and some didn't, did yours? if so does it still?)
6 Is it a millitary or civilian version ( military versions had the seat size stamped in the pommel shield civilian versions didn't)
7 Is it an Artillery saddle of Cavalry saddle? ( Artillery saddles had a D ring on the pommel and the cantle Cavalry saddles didn't This ring will look like a crupper D ring)
8 Is the saddle bag post still there?
Actually, I just took another look at your last picture and this is a civilian version saddle(that doesn't mean it's not still worth something) I noticed in the picture from the rear top of the saddle that the pommel has the civilian shield with no seat size marked on it and it never had the saddle bag post. Those are two big indicators that this was a civilian version of the 1904 McClellan Saddle. Supposedly there were more of these than of the military version but I have never seen a civilian McClellan in person ( I have seen the military version of several different eras) so I don't know if this would be more or less valuable. It would really help to know the year it was made. I wish you luck in finding someone who can acurately value this saddle for you, if you want a good guess put it on Ebay with all the info you have on it then see what it brings. There are ways of auctioning an item without selling it on ebay, then at least you will have an idea of what a collector would pay for it.
David