I found a second silver coin this weekend!
Detectorists refer to finding a "hammy". Before the 17th century coins were struck by hammering the silver flan with a die and a big hammer. That is why they are so often off-centre. Finding a hammy is the goal of any detectorist - one or two a year is a good hit rate.
This one is a half-groat of Queen Elizabeth I. It dates to around 1580. It is tiny compared to the one in the OP at just 17mm. I already have one identical to this but somebody has hammered a nail through her face. It was a time of religious strife. She was a Protestant Queen in a post-reformation England. It's not uncommon to find Lizzie coins with deliberate damage to her portrait. The owner of the estate where I live was involved in the Catholic "Rising of the North" around this time.
The two pellets to the right of the badly worn - or vandalised - bust indicates it is a twopence.
The inscription on the obverse reads "E D G ROSA SINE SPINA" which translates as "Elizabeth Dei Gratia (by the grace of god) A Rose Without a Thorn"
