Not sure what a 'Mersey' model is - I'm guessing you mean a 'Cavern' model with the two pickups close together?
Much depends on exactly which bass this is. The 500/1 Violin has been in production (in Germany) in at least three quite separate periods: original 1957-1969ish, first re-issues in late 70s through to mid 80s, and modern re-issues late 90s onwards. That's all without dragging in genuine Hofners manufactured in Spain, Japan and China.
Most likely you're being offered a '62 Re-Issue' made in the last 20 years, but DO check!
If that's the case, then it will be in classic tobacco burst, with 2 x staple pickups, and a pearloid guard. Because of manufacturing costs in Germany, the price of these has soared over the last 10 years, which means that second-hand prices have held up very well.
These basses are handmade the old way in Germany, so essentially every one is a custom instrument. They are absolutely lovely pieces of work, and a delight to own and play. They are not copies of the old basses ... they ARE the old basses, so they sound exactly as they always did back in the 60s.
If that's what you're after, then you can buy with confidence.
What they are NOT is in any way modern, or particularly precision. Intonation will indeed be dodgy in some places. That's part of the charm - they all do that sir.
Playability is great. These basses are FUN. String spacing is tighter than on a Fender, which can be an issue for some. On the other hand, they're so lightweight that they feel as if they're filled with helium.
Regular neck resets? Yup, that's right, roughly every 30-40 years. How old are you?