I'm trying to understand the location of the thru holes on the attached schematic. The image shows a mounting method for a level sensor. Any help is greatly appreciated.
A lot depends on what is 1.50"/38 B.C. and what it shows. You may want to post it too if you are looking for help at understanding the location of those holes.
Type 61 sounds enough like Code 61 to make me wonder.
Type 61 looks to be a "standard" in industries that use pipe for light duty structural service.
Not much like your image. Countersunk bolt holes for a start.
Old school prior to GD&T. For 1/4 soc hd screws. Old timers held the True position required for assembly. 3Ddave is correct. Being it was on a diameter.