Thanks Jim, that sounds very credible.
I'm green when it comes to old photo's, what does it mean "card stock"? Does it mean the format/type of card?
As I said previously, Isaac died 6 Oct 1890. I wonder if his widow, Isabella Cheesebrough Crowther, ordered a reprint of an earlier photo after his death? If there was an original of, say, late 1850/early 1860 as you suggest, what condition would you expect the original to be in after about 30 years between 1860 and 1890? Maybe Isabella just wanted a good copy of the old photo. Or would the original photographer keep the original negative and just do a reprint on new "card stock"?
I haven't given up on the original yet, but it won't appear quickly.
regards
Peter