I have no faith in that Carder book. Gardner and Carder -- I'm sad to say that I have little faith in either of these books.
I find doing the historical research on the companies and individuals involved in designing and manufacturing the objects of our desires a good portion of the fun of messing with old doubles.
It's interesting that Carder is often cited in response to wider inquiries on the internet, "Ask" type sites, non-specific to doubleguns. That book is responsible for so many makes being labeled as "Crescents", despite action, proof mark, and patent differences.
I can't deny that sometimes it has worked to my advantage.
Regards
Ken