Block oil gauge fitting
I had the exact same question about a year ago when I was putting my Tiger together. Someone here had the correct answer, which was:
it's a british fitting with a 1/4 pipe- part # bspp k4 connector --2fmk4s-
Parker Hannifin 2FMK4S
Armed with that information, I had no problem finding the correct adaptor in stock at a local hose supplier, which was not the Parker Hannafin brand, but they had a crossover chart for their part. The new CAT s/s braided oil gauge line I bought screwed right on to it. I did use about a 2" extension on the 1/4" pipe threads, which makes the line nut a little easier to get to.
Of course, a couple days later I was sorting through a box of left over hardware and found the original fitting...
Bob Knight
B9471705
B9471929