Due to a schedule change I was checking my June SFO-DCA-SFO and noticed my seats have been changed (from row 4 to row 6). When I brought up the seat map to change them back, the page displayed was very different. After a few seconds I realized this was for an A321!
Some Observations:
FC is only 8 seats. No mint-like cabin here

and a small number of seats relative to the overall size of the aircraft.
MCS is the 3 rows right behind FC. Exit rows (8 & 21) aren’t marked MCS and I was able to grab row 8 for my partner with no status.
Exit rows are a little different than I’ve seen on other A321s. In row 8 the aisle seat (8D) is missing rather than the window seat (8F). At the rear exits the window seat is missing on both sides, but in different rows (20F & 21A).
Total number of seats is 185, which is in line with AA (187) and DL (192) but they both have larger FC cabins.