[TR] caliper bolts revisited

[james mc arthur]

    Good day to all and many thanks to all that replied to my original post. 
I have made a trip out to the garage and here is what I found; now I'm more 
confused. The outer casting, the side facing me has "type P" stamped into 
it, while the back side has"type PB" stamped into it. I measured the inside 
diameter of the mounting hole in question and it measures a tad over 12MM, 
or  15/32". Am I right to think that I do indeed have  metric calipers, 
regardless of the stampings, based on the fact of the 12MM dimension? As 
always, many thanks in advance..........Jim McArthur/ CF17672U