Hello again: in my quest to reach the 30 posts so I can post in sale and trade, I hope you do not mind I show you the pics of the latest additions to the collection:

 

I have tried to find info on this Lcol, but the only references I get are from non-flying staff: any ideas so I can build the proper model for the helmet?

That's an HGU2 with the older one piece Sierra ramshorn dual visor setup. Probably vietnam Era in age. 

Concur. Early (4 screws / each side + lower metal piece on the temples area) one-piece Sierra Ramshorn + T-bayos on the MBU-5/P leads to the mid to late 60's and up to the mid 70's period for this HGU-2A/P.

Interestingly, it seems to lack the string retention for the headset, which can be explained by the presence of a black leather edgeroll (so I guess it has custom fit internals). Are the earcups velcroed inside ? Form fit liner ?

That being said, I found a photo of a Lt.Col Gene LEVY that served in the USAF during the VN war, dated 68, F-4 pilot.
Can't tell if he is the one, but at least this was an aviator from the correct era 😉.

wonderful, this is great news. The seller had some information regarding LtCol Levy and could be 555TFS, but I have been unable to find any info regarding that possibility. This is the closest. 

I will continue looking. Gracias for the help