Re: EEC Nixie Clock mystery.
In the early 1970's it was possible to get ICs of your own design manufactured in the UK by companies such as Plessey and General Instrument that offered foundry services. Plessey used to manufacture large quantities of custom ICs for a French TV manufacturer without knowing what functions they performed: untested packaged ICs were shipped out for the customer to do their own testing and/or labeling. You will find it virtually impossible to find data on such custom devices if the company who had them made is no loner in existence. The chips we designed were made by Plessey using military-grade ceramic flatpack packages imported from the USA.
If our experience at the time is anything to go by, we found that the lid of some types of ceramic package could be removed by applying a sharp tap with a Philips screwdriver. This would break the seal with the ceramic frame without damaging the chip or wiring, allowing the chip (and any manufacturer's codes it might bear) to be seen with an inspection microscope. I haven't come across that particular type of package, but I don't suppose you would like to do that.
ICs were less complex then and you didn't need a computer work station: graph paper, pencils & a ruler were sufficient.
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