Primary chain tensioner cap nut size

[pockets]

Wondering what size the nut is on 1964 A65  outer lock capnut it appears to be a different setup than the later adjuster nut ?

[pockets]

15MM deep socket fitted once  I  removed the burrs with a file , can  now adjust the tensioner.

[chaz]

one thing to remember, is if newer parts were fitted after metrification, the hexagons may be metric but should be imperial.
its cheaper to buy modern metric hex bar  than imperial to special order.

makes you wonder what will happen if , now out of Europe, as suggested we go back to imperial weights and measurements..