"PERIOD"
"Bronze Age?"
"Early Bronze Age"
"Early medieval"
"Early medieval?"
"Early Mesolithic"
"Early Neolithic"
"Late Neolithic/Early Bronze Age"
"Late prehistoric"
"Late prehistoric/Roman"
"Later medieval"
"Later medieval/Post-medieval"
"Later medieval/undated"
"Later medieval?"
"Later Mesolithic/early Neolithic"
"Later prehistoric"
"Modern"
"Post-medieval"
"Post-medieval/Modern"
"Post-medieval?"
"Prehistoric"
"Roman"
"Roman?"
"Uncertain"
"Unknown"