Ron Guth: 1811 Half Dollar are found with two different date sizes: Large 8 and Small 8. The Small 8 appears on all Capped Bust Half Dollars from 1807-1810; the Large 8 became the norm from 1811 on. Two Overton varieties qualify as Large 8s: O-103 and O-104. Both varieties are fairly easily obtained.
As of August 2011, PCGS listed 358 Large 8 1811 Half Dollars in their Population Report, of which nearly 100 are Uncirculated. The typical Mint State grade is MS63, followed by MS62. The finest examples certified by PCGS are a pair of MS66s.