I thought that I would just interject my own opinion on what most people are referring to as a suspender buckle. This opinion of course is only coming from what I have gleaned over my 36 yrs. of being in this fantastic hobby. Though it may have been used for suspenders, I believe that it was designed for pants, vests, pantaloons, etc. The webbing to go through these would have to of been 3/4" wide or slightly larger to fit in the 1" to 1 1/8" that are the common size for this type of buckle. From what I have gleaned "on pants back and vest back straps the material is sewn typically tapered with a binder inside and a facing of polished cotton on the back". Iron buckles that were japanned appear to be more common on original garments from the 1850's and 60's. (these were seen on a collection of original clothing from a personal friend who has researched this extensively) I can't imagine a fellow using such a narrow piece of webbing to hold his pants up. But then again, when out in the field they probably did what they had to do to keep them pants up.
Another reason I have this opinion of what this type of buckle was used for is because there is a reenactment supplier that sells this type of buckle on his web site. Here is his description of it........"Extant examples of this buckle often vary in styling, but all bear the raised letters PATENT 1855. We intend to produce other styles manufactured under this patent, but this is the first in the series. This buckle is taken from an original which was found on a vest back in our collection. This buckle will admit a strap of 1" and is perfect for canteen straps, vest and trouser belt backs. It is available in either black or gilt finish".
http://www.njsekela.com/OSCommerce/catalog/product_info.php?products_id=280
Also the typical suspender buckle takes a webbing of 1 1/4" to 1 1/2 " as seen in numerous dags. and ambros. I have enclosed a few pics. of some pants/vest/canteen strap buckles next to some suspender buckles I have found "out west"
These are the more common ones I find and have personally seen on the backs of trousers
Style in question and also ones made of brass not as stout as those above
Kuger was absolutely right in my opinion as these being used for trousers.
I hope I have shed some light to what these are in my eyes anyway. Everyone can draw there own conclusion and once again they might have very well been used to hold up somebody's pants as a suspender. I hope they achieved that goal!!!!
Thanks for letting me share!
IM