Thanks c_d - very helpful.
I am using 2 TATL SWUs and 2x25,000 SM for my family this summer (DL metal thru AMS, not AF), ours are coded:
MSP/PU503 - for the 2 SWUs - look correct, SWU have been "closed" in my account; I assume the "M" is for M-class, no idea about the SP
MSP/FD551 - for the 2 mile award upgrades, miles had been credited from my account about 3 days after I made the request.
I wish I had known this earlier, I got SWFU'd twice this year already - once from IAD to CDG on AF, and again from HKG-PUS on KE. Both times I purchased Y, called DL and had the upgrade "applied" (SWU for AF, miles for KE) - selected my BE seats, assumed all was good - and both times, within a month, when I showed up at the gate the airlines said I was in Y, and they refused my upgrade because DL had not yet coded it. In each case they said DL just hadn't done it yet, they didn't say it was done incorrectly.
If I had known what to look for, as I do now, I would have fixed this before heading to the airport. AF made me run to the DL counter, after an hour DL somehow figured it out, I sprinted to the gate and barely made the flight. KE could never figure it out, I called and twittered DL and they said they could not do it in time - so I paid the $500 difference for J thinking DL might be able to fix and reimburse me later. I asked DL for "credit" afterwards, they gave me 9,000 DM - oh joy
