Unidentified frame - just found out it's a Rotrax

Nice pictures, thanks for posting.
I'm new to Rotrax and only know what's out there on the interweb - but it's always nice to learn about other makes, particularly when they are well thought of and quality brands.
This frame of mine is a strange geometry (to what I would call normal), it's 23" BB centre to top of top tube but only 21½" top tube length from ctr of head tube to ctr of seat tube. The wheelbase is very short at 39¾". The angles are both 74°. It's short but tall at the same time!
BB height is 11" with 27" wheels fitted.
Probably a custom build.
Could it be an early version of the La Prima Model, showing in the 1957 catalogue with a shorter top tube and steeper angles 🤔

I keep looking to see if I can match it up but not found anything similar yet - that one you pointed me to is the nearest certainly in frame angles and the short top tube.