The reason for the multiple wrench sizes was spark plugs like the C-3 that was widely used in the 20's and 30's. To my recollection they used a 15/16" wrench to remove the whole and about a 3/4" wrench on the gland nut that held the porcelain core which could be purchased and changed while retaining the body as the center electrode eroded more rapidly.
Not arguing with you about the C-3, MShaw, but the reason for most of the sets with multiple size spark plug wrenches in the late 1930's and 40's was to accommodate as many vehicles as possible using different size spark plugs. In 1939, a Buick 8 and Packards took an 11/16" spark plug wrench, but the Buick 12 and 16, Hupmobile, Lincoln, and Studebaker, just to name a few examples, took a 1" spark plug wrench. Whereas Chevy, Chrysler and Hudson took 15/16".
Mossberg sold a nifty little set of pressed steel sockets in a wooden box with a different opening size on each end, each socket in its own slot and a narrower slot for the cross bar. I have most of them, without the box. I also have a set on a stringer from Chicago Specialty Mfg Co.
Sizes of both brands include 21/32 x 27/32, 29/32 x 1-1/32, 31/32 x 1-5/32, 1-3/32 x 1-9/32, and 1-11/32 x 1-7/16.
The US Army Ordnance Dept specified dozens of SPW's, individually, and as sets, of both types - the double end double hex pressed steel kind, and the detachable forged kind (like the Edison) during WWII. Including some crazy sizes. One was 37/64 x 23/32. Most common pairing was 27/32 x 1-1/32. Every 32/nd between 25/32 and 1-5/32. The forged extra deep socket wrenches for spark plugs came in ten (10) sizes by /16ths between 9/16 and 1-1/8.
Love to see his labs in NJ if my wife wouldn’t shoot me after the first four or five hours!
She might enjoy it. Mine did. There's a theater, a kids section where they can "invent", a shop where you can make your own recordings in a matter of minutes, and of course, a gift shop.
I cannot overemphasize how well done it is. Link
here.
