The sighting telescopes come up on ebay all the time, and as well you can still see the photos on the "completed auctions" for a time. There are also sites that show historic auctions with their photos. Once you find which scope you are after, search through those means and some sellers will show views through the scopes.
https://www.the-saleroom.com/en-gb/a...f-a4d1011ce1df