Ken Pagans of Corpus Christi, Texas, contributed a line drawing and spec sheet on the Sparrow, a 12-foot overnighter that was originally built and sold by HMS Marine, former manufacturer of the West Wight Potters (in the 1970s, as I recall).
The spec sheet credits Herb Stewart as the designer of the Sparrow. Herb was founder of HMS Marine and, I think, designed the American-built fiberglass version of Stanley Smith's plywood original West Wight Potter. Herb also designed the HMS-18, which became the Potter 19. The "MS Marine Inc." named as the supplier is apparently a typographical error and should have been "HMS Marine."
Sparrow 12 on a trailer (photo contributed by Larry Costa)
Randy Robison's Sparrow 12 (Click on image to see full-sized version)
Sparrow 16 (This one wasn't Tom's.)
He said it was very nice in all respects except that the 22-inch fixed keel required it to ride high on its trailer and made it difficult to launch.
Here are a couple of photos of one of Tom's Sparrows in the San Juan Islands:
At high tide...
...and at low tide.
A new owner of a 1975 Guppy 13 is Fran Lebowitz, who advises that the "M" on the Guppy sail stands for the manufacturer, Melen Marine, Encino, California.