Now that's an odd coincidence, I just bought one of these 'new' in the box last weekend. At least I'd assume it's the same, I don't know of any other conversion kit marked ' 38 S&W only' on the cylinder. The conversion ring is more like the Richards conversions with a captive firing pin and a rear sight on top. Mine has that same reddish tint to the ring that older Ruger frames have.
These were manufactured by Legal Defender, Inc in Conyers Georgia in the late 1970's.