Reference
Date-stamp finder
Find the production year from a blind stamp (shape + letter), or vice versa.
Estimated year
1971
◯ A
From 2015 the letters are non-sequential with no shape (e.g. T=2015, X=2016, A=2017). Confirm recent pieces with an expert.
A stamp alone cannot prove authenticity or exact year. Judge holistically. Educational reference only.