Interesting indeed. My 1676 still have the 14mm bolt for the oil filter. Though a finned one was fitted when I could get hold of one.
The smooth round one is one of the few things to have disappeared for me over the years.
Not a word about them holes in clutch centre we hear about now a days to do some extra ones of to give a better gear change?
I believe someone in this forum stated, some time ago, there were none at all in the very early CB750!
And I had in the day gear change problems. Dealer had no idea what to do.
I was the first in town to have a CB750, even the first to ask for one when the news about such a model was in the making.
I wrote to Japan for help.
Still have a polite post card dated Oct.9´69 telling me to turn to the dealer of my area, he had been informed.
Though not a word about what he had been informed!
But I never returned for any regular service after the obligatory ones from new.
Erling.