Originally Posted by
CyclesMakaron
Check around 1A for C or R; A5820 is a 1987 frame.
Piece of card on fork steering tube may contain interesting information.
Having had another look, I can't find any other letters. There are a few scratches (I'm new to Bike Forums so I can't share the images).
Looking at the fork however, I have found some Columbus embossments which would seal the deal I suppose?