It is not drasticly older, Stanley claimed in tarrif hearings that they started making folding rules in 1899 and that no one else at that time made a folding ruler....(of that general type)
I don't know what's up with Stanley. Rabone was making folding rules in the 1860's. I wish my documentation was available, but one of mine was dated to 1854, and is near identical to the Stanley folders. "A booklet about its history and use was first published by the maker, John Rabone & Sons in 1879, currently the third edition of which (originally published in 1880) is still avaliable as facsimile copy."
The invention of the folding rule is credited to Anton Ullrich reportedly invented the folding rule in 1851. But this seems to have been a version of the zig-zag ruler.
There's a book available, if you've got a lot more money than I do (starts at $45 and goes *much* higher) -- A Source Book for Rule Collectors by Phillip Stanley. The cover shows at least one odd hinge, so yours might be in there. I'll see if the public library has a copy.