Thanks for the replies everybody.
Like I mentioned, after I chose the "first class" option on Amex travel, the flight was booking into first with the same fare bases and same price.
On Delta.com this is what shows up when I look at the details:
Flight Class Date From/To Fare Basis Code Coupon Status
DL2305 P 13NOV12 SFO-MSP MA00UPRQ/XX22N OPEN
DL2209 P 15NOV12 MSP-SFO HA07UPRQ/XX22N OPEN