Frame identification help

[Coast]

A friend has been given a steel frame and forks with no decals or head badge has striped the paint off the BB shell underside to reveal L3K1662. Also rear dropout has UK GT stamped on the non drive side only. Have any of you learned folk come across this format of serial number before that will identify at least the make? Any help would be appreciated thank you

 

[midlife]

Any other pics of the frame?

 

[Cycleops]

Looks to have some serious corrosion. Maybe check for more internally.

 

[Coast]

Any other pics of the frame?

 

[midlife]

Nothing jumps out as to what it is..... long dropouts, over BB guides, Cinelli MC fork crown and odd lugs. Early to mid ish 70's maybe?

 

[biggs682]

Frame number doesn't give many clues does it
Seen quite a few different formats over the years but not seen that one

 

[Coast]

Thank you for looking. Have had a suggestion it is for a South Australian maker who branded their bikes as Ricardo. Generally mass market sold in the Supermarket with a couple of top tier models built with lighter tubing and modelled on European bikes. Aimed at the more serious amateur rider.