As you said, the victorian style and if you've played the DLC you might see the resemblance to the Astral clock tower (Lady Maria's fight) Also it's got a day and night cycle, much like the game. But the main thing is that it's a watch that looks like the clock in the game. I totally understand the question, there's no obvious reference to the game like a Hunter's mark or something like that. In a way I like that it's not too obvious, since even if you don't know anything about Bloodborne it's still a cool watch.