Dan ,
I have a similar one except it is a full .375 (3/8ths) thick. I got two , years back and they were in M/T ( Mickey Thompson) packaging . Straight 1/2" dia tube . Not a Ford part.
Randy
There were so many circa 1957-68 versions of Ford/Holley pattern 4V Ford spacers before the Boss 302. I have a collection of ones claimed to be original to some Ford or another. Some just differ in the exact size of the bores. Die cast aluminum, engineered material, tapered, parallel, four bores, two paired, open center, vacuum pick up, PCV pickup, solid except sprue locations, open except around bores and perimeter, PCV enters under secondaries, PCV enters in front, as molded, molded with secondary machining, coolant heated, and that's just what I can recall right off. That doesn't count service versions for 289s 1963-67 Ford sold to apply to more than one replacement application.
Fortunately there were not many versions used in XHP-260, HP260, and HP289s in stock 4V induction Cobras so they are somewhat simple to explain to owners and restorers.