Springfield 1878 - what have I got here? Value?

Have an opportunity to purchase this and neither myself or the buyer know much about it. Family friend (widow) liquidating her husbands old collection. We both know its old but not much more. Even if I dont buy it want to make sure she doesnt get robbed.

Here's what I think it is:
Make: Springfield

Model: 1878 Trapdoor
Serial Number: 373856
Year of Manufacture: 1889-1990
Caliber: 45-70 Government.
Action Type: Single Shot Trapdoor

Has this cool bayonet with US plate (but not sure its original). "US" font doesnt look right (aftermarket?)

VP insignia on barrel.

Anything I can pull of of it determine more about it or sense of worth?

Thanks everyone.

https://www.milsurps.com/images/impo...3/02/sf1-1.jpg

https://www.milsurps.com/images/impo...3/02/sf2-1.jpg

https://www.milsurps.com/images/impo...3/02/sf3-1.jpg

https://www.milsurps.com/images/impo...3/02/sf4-1.jpg

The rifle isn't all that spectacular, but if the sling is correct, that's pretty scarce. The bayonet with scabbard and frog helps a bunch. Haven't kept up all that well with pricing on a national level, but in my local area I'd estimate US$350-500 for the rifle alone.

Search completed Gunbroker auctions for a more national estimate. Do the same for the bayonet. Sling could be fairly valuable as well, so it would probably be best to separate the three in obtaining a reasonable price.

Thanks for the reply! Thnak you. As a learnign point, what makes the super valuable ones so much? There are several here that are either priced WAY to high or something special about them ;^)

http://www.gunsinternational.com/Spr...cfm?cat_id=367

Condition and scarcity are big factors. Most "average" trapdoors stay local.

ser# puts that rifle at 1887 mfg year,there is no such model as 1878,look close with a magnifier, your 8 is a 3
here is a good link for any and all trapdoor info.The U.S. Springfield Trapdoor Rifle Information Center