I run the NEONIXIE-L Google Group - we've been doing nixie and related stuff since 2002, originally on Yahoo and since 2010, on Google - just under 1,000 members.
So, I did a bit of research. European Electronic Counting definitely had custom chips made for them by Emihus Microcomponents Limited (also known as "EML"), a UK company based in Weybridge, Surrey with a manufacturing plant in Glenrothes, Scotland. Emihus, was an LSI manufacturer specialising in calculator chips, jointly owned by EMI (Electrical and Musical Industries, 49%) and Hughes Aircraft (51%)...
I've found references to the EML HEEC2, also known as the EDC 6051 and EDC 6052 (depending on options) - these are timer/counter LSI devices. There's an article in ETI, page 62,
http://www.americanradiohistory.com/...ay-1975-08.pdf however, the clock is from 1972, so it may be an earlier chip. Emihus tended to prefix their part numbers with "H" and I would assume that the initials "EEC" in the part code are not coincidental... There's quite a lot in the trade press about EML around that time frame (1968-75).
Therefore thinking that this is where the device came from. Now to identify it!