My latest lamp is a vintage Crompton MA mercury lamp.
It came from Ebay and I didn't think I would win it - I put a last minute bid in and won. I didn't look that closely at the listing and it wasn't until it arrived that I realised it was a low pressure MA lamp - which means it must be run cap up. The dark coating on the cap threads are a graphite coating to prevent it binding in the lamp holder.
The box is in very good condition, but there are a couple of very interesting things about it.
The Royal crest refers to the "late King George VI" which means it has to be post 1952 following the death of the King.
However, the end of the box carries a Nato Stock Number (NSN).
This form of NSN didn't exist before 1975, so it looks like old stock on the shelf was "codified" with a NSN. By 1975 the MA lamp was well and truly obsolete, so I am pretty certain it predates that. The 996 6738 part of the NSN is reproduced on the lamp cap.
The lamp has a date code which translates to May 1957 or May 1965. Given the reference to King George VI, I am pretty sure it would be the former. By 1965, MB lamps were well established, so again it would suggest the earlier date. The lamp is also engraved with "Property of HM Government". This appears to have been etched on at a different time to the logo which would back up the theory of old stock being codified.
Further evidence of this being a May 1957 lamp is provided by the brilliant Lamptech site. That lists a practically identical lamp - only the logo is different - the date of that lamp is
June 1959.The box is also the same, the crest appears to be the same, but unfortunately the text is too blurred to read. The text layout is slightly different but I can just make out what looks like George VI.