I would fully endorse the 600 and Dean's book on the subject, which is well worth the cover price.

I've managed to trace original copies of the contemporary reviews included in the book as my eyesight is not good enough to read the reproduced copies, as well as some others from The American Rifleman and Gun Digest from the 1960s. I also have a manual with one of my pistols that is a cross between Dean's variant 12 and 13, so maybe it's the 12a or 12.5

I'm handing my Sears marked 600 to Lawrie at Kempton tomorrow for a service and am already looking forward to getting her back for a range session.

John