Only 5 Proof 1827 Half Dollars are known to exist.
Four are from the O-121 die combination:
PCGS PR66CAM. Philadelphia Mint - Joseph J. Mickley - Reichardt and Reakirt Families - Columbus Stamp & Coin Co. in 1962 - Mrs. R. Henry Norweb - Bowers & Merena 11/1988:3088 – Bowers & Merena 5/1993:293 - subsequently graded PCGS PR66CAM
PCGS PR66. George H. Earle - Henry Chapman 6/1912:2927, $5.50 - John H. Clapp 1942 - Louis E. Eliasberg, Sr. - Bowers & Merena 4/1997:1831 (as raw “PR65)”, $110,000 - Heritage 1/2004:2078 (as NGC PR68 675313-007), $126,500 - Goldbergs 2/2006:1468 (as NGC PR68), $178,250 - Texas collection - subsequently graded PCGS PR66
PCGS PR66. Stack's “Auction ‘83” 7/1983:690 - Superior 1/1988:1768 - David Akers “Auction ‘90” 8/1990:1599 - RARCOA & Akers 8/1991:532 - Heritage 8/2011:7157 (as PCGS PR66 19749809), $161,000
NGC PR64. Heritage 6/2001:2309 (as NGC PR64 676841-002, not sold - Heritage 11/2001:5883 (as NGC PR64 676841-002), $29,900
One example is from the O-107 die combination: PCGS PR64. Breen Plate coin. Heritage 8/2007:1682 (as PCGS PR64 10950676), $80,500