PF-61 or PF-62 would be generous, I don't see enough rubbing really to justify bumping it down to AU, but its certainly in the lower grades.
Its not bad for being circulated, but proof coins pick up scratches and scuffs a whole lot easier than circulation grades. With the same handling methods, a business strike coin might grade within the mid MS-grades, but proof coins are very easy to damage.
When you can pick up a PF-68/69 example for $10 graded, its not really worth sending in. Of course it only costs 5 cents to keep so by all means keep it for your collection, but its a fairly poor proof example.