
Well turns out its almost guessable Scottish Brick Company is the answer. Around 1969, saw the NCB selling off its brickworks with the Scottish Brick Corporation (SBC) taking over most of them in Scotland, some 33 sites.. The SBC then started using its own stamp on the bricks it produced, usually the initials SBC. There are various designs of stamp that differ in letter, frog and marks and it is very possible that each site marked their bricks slightly differently in this way.
Plenty of detail as usual on the Scottish Brick History Website
https://www.scottishbrickhistory.co.uk/ ... 20Scotland.

Regards Neil