Small printed name on my 'Strike Ruler Mk 4' is Blundell Harling Limited, see link below;
Drawing Boards from Blundell Harling
Ref number on the cardboard cover is 6605-99-110-5768. However, the ref number on the ruler is 1680-99-6379347
I also have a 'plotter, combat mission, plu-6/c'. The NSN is 6605-00-766-6901. This is a USAF version of the Strike Ruler made by Aero Products Research Inc, Mfr's Part No FAA-215. If you Google the NSN there are other manufacturers listed.
Hope that helps
G&J
I know that the 'original' strike rule and the Buccaneer protractor were acquired at the begining of the F4/Buccaneer acquisition. It is quite likely that the RAF F4 crews had copies of the USN rules made.
I know that they visited the LNP Co to ask for a quote to make the rules. They were asked how many they wanted. A quick finger count ensued with a total to match the number of aircraft ordered and an allowance for breakage. A figure of a few hundred was reached.
A bit like the Apprentice, the company laughed and said they had been thinking in the order of 100,000. The cost of material was minimal and they could produce that number in a day. The cost was in creation of the moulds and the cleaning up afterwards.
I don't know how many were ordered in the end. I hope it was a 100k.