Cards by Rank Precision Industries

I am grateful to Peter Gill who has informed me that it is likely that the cards that I describe here come from the Xeronic printer, a technologically advanced non-impact page printing device developed at the Rank research labs in 1958/9 and manufactured at Shepherds Bush, London. Unfortunately the device was quite expensive to purchase and maintain, and it was not a commercial success. There is little information on the Web about it, so if you recognise this card or can tell me anything about it, or you know anything about Rank digital devices such as the Xeronic printer, please

I have a number of cards like the one shown on the right: click on the thumbnail image of the card to see a larger version (50KBytes). The card is brown paxolin and measures twelve and 1/2 inches by five and 1/2 inches: a large card. It bears seventeen Newmarket V6/8R transistors and seven Mullard OC139 transistors. It is clearly a logic circuit of some kind.

Features of the card that are very characteristic and would help identify it are:

Its unusual size, its sparse population, and the high ratio of transistors to passive components.
It has a 7/8 inch diameter hole at the end opposite the edge connector. For this to be used to extract the card, the cage cannot have held the boards too close together.
It is marked "TYPE ZX1030", "RANK PRECISION INDUSTRIES LTD" and bears the Rank logo of a man striking a gong.
I have a number of similar cards, all with ZXnnnn identifiers, but some are marked "RANK DATA SYSTEMS DIVISION"
The cards use transistors from Mullard, Newmarket, Semiconductors, and GEC : all British manfacturers.