Moon from 27.02.2023

And how did they attach a Barlow to it? Was the 1.25-inch standard already in use back then?

Yes, here you go.
Its aperture is 57mm. The focal length is 800mm.
The tube is brass with bronze. The objective lens is an achromat made from various types of glass. It is handcrafted.
I believe a photo of it was on my page.

No, it wasn't there yet. It's all a bit complicated, but possible. I attached the camera to a small ball head that mounts onto an adapter for DSLR cameras, made of several plates—you probably know the type. It also attaches to the eyepiece holder, and you move the camera toward the eyepiece to get focus. So, at first, I managed to just press the camera against the holder like that. But then I replaced the plate between them with a longer one, and that made it possible to insert a Barlow lens too.

Thank you very much for your feedback)