Very Weird Proto Socket

[dimwittedmoose51]

Been away too long folks, but this one deserves the guru treatment.  Been collecting Proto and Plomb stuff for quite a while, but never seen this socket before.  Dug it out of a pawn shop bin.  It's a Proto 5016H which if memory serves, is a 3/8" drive medium deep well 6 point 1/2" socket. The 5016 was the 12 point.  Right behind the "1/2" in. stamping from the factory is a minus sign and then the Greek symbol for Pi.  The socket itself has some sort of brass or bronze sleeve pressed down in it.  The sleeve goes down about 3/4" or so and then either has some stops that are forged into the socket interior walls (presumably to prevent the sleeve from going further down the wall length) or they are some sort of appendage to the brass sleeve.  The sleeve appears to have no threads or other additions to it and I'm pretty certain this isn't some sort of stuck nut inside the socket. Photos of the lettering and the actual insert were really tough to get , so I apologize for that.

Anybody have any idea what this insert was supposed to do?  Nothing I can find on the internet so far.  Thanks all!!

DM&FS

[john k]

Been absent myself and just saw this.   The brass liner tells me it was to protect a polished surface or very fine threads.  The hex is deep enough for a nut, to be run up or down, am thinking it was a special tool for a machine that had a threaded adjustment, something that could in no way tolerate the threads to be buggered. 

[dimwittedmoose51]

Thanks John!!   The email response from the Proto CSR didn't haave near that amount ofinfo in it!!

DM&FS

[Twertsy]

-H is just the designator for Hex (6 point).  Look at any Proto 6 pt. socket.  I'm betting someone had a need for that insert and put it in there.  Otherwise, there would be a specialty model number.

As for the greek symbol, those were used as date codes in 2000 - 2002.  See date code list here: http://toolarchives.com/node/231

[dimwittedmoose51]

Thanks, man.  That inseert certainly looks like it's from the factory......

DM&FS

[Twertsy]

I suppose it could be.  But, what I've seen is different model numbers/designators on all specialty sockets I have or have seen.