Can't upload a pic.... they're too big for this website...

Make them e-mail size.

They may have measured from the bottom rim of the drum, as opposed to determining the center by measuring from both edges?

There were movies (8mm) shot by Bill Ludwig Jr. in the factory in the mid 60's that used to be available on youtube (I think they are gone now). One scene shows the worker drilling a floor tom and he "freehands" the hole for the badge. No jig, no measurements, just bang, there's a hole and here goes the badge and grommet. Looked like he got it about right. Not to say that there wasn't a jig or other sort of placement aid that they were supposed to use but if you were drilling a couple hundred of these holes a day, five days a week, you might tend to skip anything that slowed the process down, and you also would get pretty good at eyeballing (almost) the right spot. Must have been or become pretty standard proceedure, figure the big boss was actually filming him and he did that anyway.

There was a thread not long ago about crooked and/or off center badges on one of these forums and there were LOTS of pictures of vintage drums with that issue posted as a result. Ludwig and Slingerland both.

With the production levels Ludwig had the guy could eye it well and the jig would cut his production level. It`s probably the last step. Then out the door