Congrats on a neat find.
I purchased this recently... Once it actuated that, it allows for viewing 15 stereoscopic cards...
Many companies made coin-operated stereoviews, often countertop and sometimes floor model machines. Some had one card set to view, others had 4. Many operated on cards (like this one), some on glass slides. A few had really weird mechs like where one card is chained to the next in a big loop rather than the likely more efficient spindle wheel this one has. Of machines that take cards, common numbers included 10 at a time, 12, and 15.
I was surprised of the manufacture date of 1896.
That is when this company first started marking these. They were made for a number of years. However, the company changed their name around 1900 apparently, so your machine was likely made between 1896 and 1900.
... Most of my cards were in bad shape. There is some French guy selling versions of them. I am basing my listing off of those...
The auction you linked to seemed a bit expense. Note that cards come in different sizes so just because you see a set on eBay doesn't mean they will be a perfect fit. Note some cards have a slight curve, likely for the non-coin-op hand-held viewers. You don't want the curve ones for your machine.
I just got my copy of Automatic Pleasures in today.
Automatic Pleasures, published in 1988, is still the best book reference for for anyone interested in -vintage- UK coin-op arcade machines. Nic Costa, the author, ended up moving from the UK to the country of Cyprus. He published another book or two which are basically photocopies of old ads and more -- the production quality slightly disappointing.
In 2023, he released a new book "Penny in the Slot -- Conceiving the Internet - the Birth of the Coin Machine 1735-1883. I have it on the bookshelf hear but haven't had time to look at it yet:
My lock does not look to be original. It does seem to be period correct. It takes a flat key that was very easy to make a replacement.
I need to learn out to pick these locks. I've seen some concepts, but I've not had much success yet. I find (relatively) modern locks easier to get into it.
Yup... typical of these machines could be 10-15 frames every 30-60 seconds! Unlike the Mutoscope, released around the same time, which is typically (depending on how fast you turn) plus or minus 15-30 per second -- way faster.
I like finding the odd and unusual coin-op. I would say that this fits both.
I like the old and unusual machines too

.
...Looks cool though. I remember the Cliff House used to have some entertainment like this down in its arcade (rip). Its a shame someone molested it to do free play though, prob a irreplaceable part at this point...
The arcade at the Cliff House basement was Musee Mechanique. After they got kicked out, they moved to Pier 39 in a touristy section of San Francisco. It's still there:
The good thing about this old stuff is that they are easy to make parts for if you have an understanding about how it is supposed to work.
Indeed!