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Sometimes the CIIG mark was put on a piece that was experimental, or had been made in training, and was then sold in the factory shop (rather than just being a sub-standard piece). So, for instance, your example might be from someone learning how to make a spatter ground. Regarding date, I think there is little to tie it down to a particular time frame (the CIIG mark was used for a long time) - but you may well be correct with 1970s.
Alan