Your processes

[MattKing]

How did you fit a 35mm 55 mm lens to the enlarger?

I would guess that the lens is a 42mm screw thread mount, and that the enlarger has a lensboard with a 42mm thread installed on it.

 

[Paul Howell]

I would guess that the lens is a 42mm screw thread mount, and that the enlarger has a lensboard with a 42mm thread installed on it.

If the lens is labled Pentex it is a K mount, not M42.

 

[Monito]

If the lens is labled Pentex it is a K mount, not M42.

Well there you have it: "Pentex" for K mount, and "Pentax" for M42. Except there are Pentax K mounts as well.

The Pentax brand is an old brand.

 

[MattKing]

Well there you have it: "Pentex" for K mount, and "Pentax" for M42. Except there are Pentax K mounts as well.

The Pentax brand is an old brand.

Actually it is neither - according to the OP it is labelled: "Asahi Opt. Co. - Super-Takumar 1:1.8/55"

The OP understood that to mean a Pentax lens when he made his opening post.

 

[nightbringer]

It came with a Pentax lens cap, I'll get some photos up once I get home and get an opportunity to photo my enlarger head.