Antique shop and quite expensive... but still courious. I didn't get to touch it but what I know is that there is only capital letters and the silver thing seem to be a extension of thd space bar. There is one key thay says MS, which reminds me to the calculators but it could be whatever.

This is a machine to produce stencils for the Elliott Stencil Machine. its rare to find these.

Very neat. It looks like a variant of Underwood's 'Fanfold' machines set up to handle a specific form. The large metal key might have been the automatic paper advance that would have spooled out the completed form and set up the next one in line. I've read about Fanfold models being used as part of a company's order taking process, but I'm sure there were many different uses/requirements for such machines and it wouldn't be a surprise if this one was custom ordered to handle one specific company's needs.

​It would be interesting to know if there are any other markings or stickers on the typewriter, and I'd also be curious to see what the back of the machine looked like.

If it's in an antique shop you could always offer a much lower price. I've done that numerous times with decent success. The machine may have been sitting in there for years and the store owner might be happy to just get rid of it, especially that it can't be used as a practical typewriter and would only ever appeal to a collector who wants an unusual ornament for his shelf. I'd probably pay up to $90 for the thing, but that would be pushing it. And if you're going back anyway, please take more pictures!