I have these catalogue pages courtesy of another forum member (can't remember who, sorry!). They date from around 1980 which, going by the frame number on yours, is probably the right time.
I think that the customer selected the tubing, lugs, forks crown etc. and had the frame built as required. The shop possibly decided on a spec. for stock frames and sold them as such.
Somewhere in some magazines from the period I have some more MKM adverts which I will scan and post when (if!) I find them.
Post a photo of yours please!
Today is the yesterday of tomorrow.