For the difference in money you would pay on ebay, hold out for the 520. Its better made, probably with better pads and more care and attention to detail goes into making it. It also has ribbed construction, meaning the posts are attached to ribs that are attached to the body...this makes for much better allignment of the posts (and rods), and a more heavyweight construction.
Based on the info on the website there is no mention of a detachable bell on the 500 (and the picture is inconclusive) The bell on the 520 is removable, so if there is a dent in the body, its potentially much easier (and cheaper) to repair than the 500 if that one is soldered on.
The annealing of the body perhaps maybe also accounts in part for the very solid tone that my 520 gives...I havent played a 500, but many cheaper / student horns have a somewhat thin, uninvolving tone.
Based on the info on the website there is no mention of a detachable bell on the 500 (and the picture is inconclusive) The bell on the 520 is removable, so if there is a dent in the body, its potentially much easier (and cheaper) to repair than the 500 if that one is soldered on.
The annealing of the body perhaps maybe also accounts in part for the very solid tone that my 520 gives...I havent played a 500, but many cheaper / student horns have a somewhat thin, uninvolving tone.