Maybe a common TYPE of overstrike, but I wouldn't call this coin a common overstrike. The peculiar way the undertype legend has come through is very unusual.
I am no expert in the minting of coins and definitely not overstriking a coin but I cannot understand how the original
legend has been left behind so clearly in parts. I assumed at the very least the original
legend would be flattened to some degree or some sign of the new
legend would be present.
The BM seems to be keen to know if it
had a
mintmark so not sure if they are trying to perfectly attribute the coin, understand the process of this
overstrike or even if a certain
mint in
Roman Britain is doing this.
Its a puzzle which is clearly beyond me
Thanks
Steve