"Serial numbers that begins with 10, followed by a space and then several other digits. This system was quickly replaced by a second convention, although instruments bearing these designations were produced for a few months in late 2009 and early 2010.
Serial numbers that begin with “US” and “MX,” followed by two digits that denote the year and then several other digits, thus denoting the country of origin and the model year (a serial number starting with “US12,” for example, would describe a U.S.-made instrument built in 2012; “MX10” would describe an instrument built in Mexico in 2010)."
This is from Fenders serial number decoder page