Major Mint Errors on the 1oz Gold U.S. $50 American Eagle series are very rare. There are only a few known that were struck with partial collars or broadstruck out of the collar. This $50 Gold Eagle was double struck and has a partial collar with reeding on both edges. All double struck U.S. gold coins are extremely rare and highly desirable by collectors.
Below is a close-up showing the two sets
of reeding since it was double struck:
Here is a 1986 $50 Gold Eagle Broadstruck,
that was featured in Mint Error News Magazine:
Gold Errors are featured in chapter 12 of the
NLG Award winning book, World's Greatest Mint Errors: