I was at a local gun show a couple of weeks ago. I was talking to a vendor, who had what he claimed to be genuine mil spec surplus parts. I saw the packages that some of the parts were in, and they did look to be old OEM wrappers and parts. I got a few parts from him, as well as a business card so I can remember who it was. I did grab a bolt release that didn't really look to be anything special, but it is stamped "MFG xxxxx" with the X's being a 5 digit code number. I have purchased other OEM parts that had similar markings as to the mfg of the part. Is there a way to de-code the mfg code number to see if it is genuine?

Sounds like it might be a CAGE code for gov't contractors. Try this link

https://www.logisticsinformationservice.dla.mil/BINCS/begin_search.aspx

google cage code xxxxx

Evidently it is a valid manufacturer of US Mil parts. I found an ARFCOM thread with the same part in question in the archives.
http://www.ar15.com/forums/t_3_118/420917_ID_This_LPK__andamp_quot_MFG_74770andamp_quot_.html
I guess it means my "disconnector" is real too.

Anyone can apply for and receive a CAGE code.  Doesn't mean they've ever received or filled a military contract, just that they have a CAGE code.

For it to be real government surplus, there should also be a contract number on the packaging, which will identify for whom and under whose purchasing authority the contract was given, and that can be looked up in the federal register.

I think that is Mattels  CAGE code....

Many of the Magpul fanboys over on the magazine forum have convinced themselves Pmags are USGI because they have NSN's and CAGE codes....

Same thing with the Tapco Fucks....