Advertising covers related to artificial limbs, while perhaps morbid, were a definite fact of life in the years following the Civil War.
Most recently, a weekly postal history blog, I suppose you would call it, described a cover similar to this one, along with a good deal of background on the subject of artifical limbs.
Postal History Sunday is a weekly online column, written by Rob Faux, a postal historian and a bit of a modern Renaissance man, whose writings I follow regularly, and enjoy thoroughly. His column #299, titled
Out on a Limb, can be found here.
All of his previous columns can be found here, and cover an amazing broad range of subjects. Give them a try.
MikeL
https://postalhistorysunday.substac...ut-on-a-limb