Brad, thanks for the input and comments.
I got this reply from Larry Hatfied:
"believe it was built in the late fifties. you can tell it was made when we still used a tapered round rasp to shape the grip area under the shelf. and that decal is pretty old. pearl had her own method for serial numbers at that time, so I do not know how to read that. the bowyer number is #6, but the next number could be the month. sorry I can't be more help."
BTW, finding old bows and researching their origins can be entertaining, but also time consuming...and frustrating.
Over the weekend I picked up another Howatt which I know is from the 50's. It has leather grip, 58" long, and the number "48" stamped in the sight window. The decals and lettering are missing but I'm thinking "Mamba Hi-Speed". Glass on back and belly is tan color and woven.