[77T]

William
You have accurately described a "Bluesy" Sub but don't know if it is original or not without many details. We can't even tell from pictures if it is genuine or a "pieced together" Sub from different parts.

Things you can check are whether the bracelet clasp has a fold out divers extension in it. If not the bracelet may have come from another model. Even if it does, we have no way to tell if it was a replica bracelet without lots of close up pictures.

The dial could be a refinished one, plus the blue bezel insert could be a replica.

With no papers, you won't know if it started life as a regular black Sub or is a true Bluesy.

Bottom line, take it to an AD for verification. If it checks out 100%, the price is fair as long as it is in good condition inside and out. I just sold one exactly as you described for $7K on eBay - it was a full set though with all docs, etc.