Those are Bridgestone's die cast aluminum lugs. That and what appears to be a nude, stainless steel, seat tube has me leaning towards a Submariner variant. The lugs were brittle and there was an issue with binder bolts ears cracking on the seat lugs, so they eliminated the ears and went to a seat post with an internal expander bolt. The seat lug on this bicycle still has the ears so it's early to mid-1970s and I'm leaning towards the latter based on the stem mounted shift and brake safety levers. The Altus front derailleur would appear to be a replacement, as the shift levers and rear derailleur are period correct SunTour and the Altus is too new for the bicycle.

In America, the Submariners typically came with aluminum rims and all three main tubes were nude stainless steel. These rims look like steel and only the seat tube is nude, so that's why I'm calling it a variant of the Submariner. It would be interesting to test all three main tubes with a magnet to determine their degree of magnetism. Also, the serial number should reveal the exact year of manufacture.

Photo assist...