The dual price thing in France was supposed to end in February 03, but many shops kept it going long after, especially at market stalls. Older people in France were still having problems with the Franc being changed so that 100 became one. Imagine the problems in the US if $100 suddenly became $1.
Big supermarket in Strasbourg.
I think it’s interesting how quickly inflation would have dealt with so much of the issue anyways, even if there had been no change. The ha’penny was already worthless by 1971*, the penny would have gone by the early 80s (like the 1/2p coin that was its closest replacement), and after that it wouldn’t have taken a huge amount of time to completely erode anything smaller than a shilling as a useful unit of account. And once it was just pounds and shillings, decimal currency would have been a minor change in notation.
*IIRC the plans at one point included an aluminum 1/4p coin to replace it, but that was completely unnecessary by the time the decision was made.