Updated: Nov 14
The tale of the clamshell holster begins simply enough then tangles at the end of WWII. The Jewett factory burned in 1944 and was rebuilt, yet the name changed to Stanroy around that time and a man named Gresham started up Safety Speed making the clamhells. The PDF has some outdated info in it; the Stanroy name's origin remains unclear because it was not the widow Jewett's maiden name as in the PDF, and it was Jewett's principal partner who made the Jewetts and the Stanroys. Somewhere in that mix appeared Hoffman and nowadays we know the style best because of Adam-12 on television.
The CHP even banned the holster, grandfathering the existing uses:
CHP then switched to the forward draws of Hoyt and by the '70s to Bianchi's then Safety Speed's own forward draw that was IMHO the best of them all (better even than the Bianchi 27 from which it was derived):
Which configuration generated conflicting patents issued the same month to one of the Clark sons and to Paul Boren who had owned/operated Safety Speed since founder Gresham died. Looks like Boren won that round because the Clark iteration appeared only as a Thompson Leather Goods product then never again.
Read more about the clamshell's place in holstory in my book titled "Holstory -- Gunleather of the Twentieth Century -- the Second Edition" available at www.holstory.com .