Incidentally the DTL 945 flip-flops came from a grab bag that I bought as a schoolboy from Bi-Pre-Pak in the UK. There were several shops like this in the UK and the US that advertised in hobbyist and professional magazines. Sometimes the chips were surplus, sometimes seconds from the factories. Here is the first page of the leaflet that described what I got. The other pages have the pinouts.

There were also 8 chips that were marked BMC926 which were not described in the leaflet and I couldn't identify from any databooks. In fact the DTL series started at 930, the earlier ones being RTL, so that was puzzling. I have been in the dark for decades.

Today I had a hunch that the last 2 digits were transposed, and the number should be 962, which designates a triple 3-input NAND gate. It has the same pinout as the 7410 so I selected that in my tester and lo and behold, they passed the test. An old mystery solved, even if it's of no practical consequence. Incidentally together with the 12 945 flip-flops, it means I must have bought a bag of 20 chips since I haven't used any of them until now.

A search for Bi-Pre-Pak gets a few hits. One is of the managing director who retired in 1987 so the company would have been trading up till then at least. Another is of somebody who designed an audio power amplifier for them. So here's another retro-tale for the search engines.