The $50 gold pieces issued by the United States Assay Office of Gold in San Francisco in the early 1850's were not actually coins per se. Rather, they were called "ingots" at the time; today, we know them as "Slugs." Their real value, besides that stated on their face, was in standardizing the jumble of over-valued, underweight, and off-purity private issues prevalent at the time. Nowadays, the $50 slugs are among the most popular of all California gold pieces.
High-grade examples are very difficult to locate. Because of their high intrinsic value, the large majority of them have been melted down over the years. Those that entered circulation were subject to all the injuries that a heavy gold coin might receive, especially bumps and bruises on the corners. Because of their high numismatic value, many have been repaired or otherwise "improved" over the years. Finding an example with original "skin" and that crusty, old-gold look is well-nigh impossible.
Typical minor nicks highlighting the fact that these coins were actively circulated.