Strange reamer designations

[Jonathan Coates]

Well I got a reply from Presto which confirms that these were specially made for a customer, but they can't give me any details as it predates their IT system and all the paper records are long gone.
Looks like a hole will have to be made then.

 

[Wonk]

I have some such reamers in my tool box that were picked up years ago at a garage sale or auction.
I estimate the size and drill a slightly smaller hole in some aluminum plate ( 3/8-1/2 ") and then carefully ream the hole and measure it and then put a tape wrap with size on the shank.
You want the work piece thick enough to use a telescopic gauge for measurement
Rich

Gauge pins would probably be even more precise if you have the blessing of owning them.