Just a guess, but the "H" could stand for "heel" to show what direction the bridge should face.
You know, it could very well be. I would have used N for neck or T for tailpiece.
I was hoping that it was made by someone famous like Oliver Hardy or Thomas Hedison.
Is it a "Huber" bridge?
It's neither Huber nor Hatfield. Their logos are different.
Didn't think either would use a pencil, unless maybe an early prototype. Didn't get a pic to come through.
Here's a copy & paste that might come through.
'Thanks to Bob Smakula' 47 min
'GROUPS' 1 hr
'Movin' on up... ' 2 hrs
'Gentle On My Mind' 3 hrs