It seems like I remember hearing that at least one or two other custom gunsmiths built them as well. They were a hot item for a while there, but not all that many of any one type were ever made.
Froggie
PS to Add: In the back of my very old amphibian brain I seem to have a vision of one of these being built by Austin Behlert. He was better known for other things, but he seems to have dabbled in a variety of things.
Also, wasn't a feature of the ASP the so-called "guttersnipe" sight groove milled into the top of the slide? There was lots of discussion both pro and con about that feature.