Rson1982, posted: "I actually have the same question. I came across this coin and it is the exactly same double sided eagle that H3RO mentions above. Unfortunately I can't find any information, which makes me think it may be just an imitation coin and mostly likely much more recent than 1850. Any information is much appreciated." Go to Google, type in: California Facsimile Slugs.
Thomas J. Jankovsky wrote a book "A Reference Guide to So-Called Slugs and Facsimiles" in 2008 which has these items in it. Mr. Jankovsky's website: http://www.jankovsky.net/html/slug_facsimiles.html He listed several "slugs" similar to Rson1982's pictures which have the same double-sided eagle. They were struck or cast in different years from around 1915 to the 1960's. One was graded by NGC (Numismatic Guaranty Corporation) and the NGC container legend for it is: (C1915) CA GILT $50 MEMENTO - HUMBERT SLUG TOKEN MS 61 TYPE 1 1819146-008 When I looked up the number on the NGC website the pictures did not show. Rson1982's slug might be one from the 1930's or 1940's but one would need Jankovsky's book for more information.