TWO 1872 Daily Prayers for American Israelites Cincinnati Ohio Jewish Books

Description

Each dated 1872, each are identical in number of pages and content. Both have gold-tipped edges to the pages, no pages loose or missing, no writing on any pages, no loss to any pages.
My expertise lies in old Jewish objects, not books. I have no idea what the market price for these are. I entered the title in a Google search and a match came up from a book dealer in California where his price is ,000. So lets say that's "high retail", what is the value, half that? Also, why is one book much slimmer than the other? And why on one outer book spine edge does it say "Prayer." and the other "Prayers."? Is the "Prayer." version more rare?