If it was me, and this was the bass I wanted, I would…
Play it.
Check all the knobs.
Check the tuning machines.
Check the truss rod.
And then, if everything checked out, it felt good, and I was comfortable with the price, I would go for it.
Other than that, you can call Fender directly and ask them about the serial number. I’ve called them a few times and they’ve always been very nice to deal with.
@eric.kiser I did buy it–but not at $4k. It was in very good shape, just a few usual nicks. It sounds great even through my little amp, with the resonance and sustain my MiM J-95 has. I contacted Fender, but it’s not in their database. The rarity of the five-a-side style (as the Dimension had at this time) suggests that it’s a FSR? As I’m in Latin America, quien sabe?
I’m wondering if someone hasn’t changed these tuners out for a different model. You could send that pic over to the techs at Stew Mac (guitar parts and supplies) and I bet they’ll know what they are. Those guys are great.