G'day all.

I've lately started up a collection of image orthicon camera tubes as I am interested in building a working camera out of them using modern solid state electronics or using original valves going by a Marconi MK3 circuit design I have. I have sort of talked about this in my previous thread http://videokarma.org/showthread.php?t=246979 .

I have obtained two 3 inch IO tubes from the 50s won in Ebay auctions, one a RCA 5820 and the other a General Electric GL-5820.

Anyways I would like to be able to get an exact year of manufacture on these tubes and I was wondering if anyone knows how I can date these camera tubes going by the printed/engraved numbers on them. Here are the given numbers:
RCA 5820: V3711 (also there's another number which is 4001)
General Electric GL-5820: 66781

Here are some pics of the two tubes below.