Cool speculations.That is a strange one simply because the parts do not fit together. The neck is not the neck that was usually used on the 500/2 and those pickups are not standard to the 500/2 either. So I think there are three possibilities:
1. It was made by Hofner initially back in the 60s. They were overwhelmed with orders due to the popularity of The Beatles and they often struggled to keep up. That is one reason the 500/2 was made. The could could not keep up with the demand for 500/1 bodies. So sometimes things were thrown together and sent out the door.
2. It is a custom shop bass. Folks can order custom shop basses from Hofner. This could be the result of that option. The pickups make me think that is a real possibility, but the neck not so much. I don't think that neck is an option for custom orders.
3. It is a Hofner parts bass put together by someone else along the way. Hofners are not as modular as Fenders, so we don't see Franken-Hofners very often, but I have seen them. So it could be a Hofner that has been altered over time. All of the parts do look legitimate.
My two cents anyway.
Whatever the truth is, I'll treasure it.
On the other hand... I hope it's not 3

