A 1971 Deep Sea. The bezel appears to be that of a typical B model as I haven't seen my example model with the what appears to be a pepsi bezel. It is indeed a deep sea bezel and correct age. Perhaps a swap sometime or maybe was fitted with it originally? I have seen a B model with the typical plain bezel though. The movement shot shows the Valjoux 7733 markings as well. Recently serviced and working beautifully.
Here is a list of all the early 70s models. 3 Deep Sea chronographs and 5 standard chronographs. Looking at the model numbers you'll see they all are part of the same grouping.
The more I look at this watch the more I see a mix match of parts between the 31001-1W and the 31003-7W (B).
Your watch has the crown, dial, hands of a 31001-1W, but the case and rotating bezel of a 31003-7W (B).
I think someone has put the guts of a 31001-1W into the case of a 31003-7W.
Meaning it's not a true "B" model so I'd just called it a Bulova Deep Sea Chronograph.
Yes, technically the "B" had a Tachymeter, the rotating bezel is faded but I think correct. Here is my example, I suspect the dial is a replacement as the markers don't match as well. I'm comfortable noting the possible swap and receiving this one into the dB as 1973 Bulova Deep Sea Chronograph B. I'd also be comfortable leaving the "B" off.
At the risk of being a tour guide to the obvious, I note that it's odd Bulova would designate what is clearly a race timing watch as a 'Deep Sea" and put a "dive" strap on it!
In reply to Yes, technically the "B" had… by Geoff Baker