UK 5 Pence 1978 - Flatter hair with deeper detail

There seems to have been a change to the way the 5 Pence was minted in 1978.  My coin has much flatter hair with deeper detail than coins minted before or after this date.  I have no other examples to compare mine to, so could this be a variation or a one-off for this year?

The same variation can be seen on the 1979 and 1980 10 Pence, with detail above the tiara that doesn't appear on previous issues.

Please send us images of your “flatter” coins?

10p version - flatter surface on 1979 coin in comparison to 1975.  It's almost as if the groves are square cut and the raised sections are flatter.  More difficult to show on the 5p as they are quite small.