Hey Pallewheel, I was fascinated to read this post and it raised some questions about my Sekonda 3017 and I wonder how you (and any others here) would read mine? When I bought it @Odessa200 suggested the balance bridge may have been replaced as he wasnt sure the early number fitted the later watch - It has 19Jewels in English, 3017 stamping, but bridge is a low 15509
Perhaps in an un jewelled watch, the balance staff broke, easier to slot in a whole balance+bridge than repair and the watchmaker sourced an earlier bridge/balance???