Of course I don't know if it has any bearing, due to their "age", and possible "history", but I have noticed a few things.
Starting with "AE" prefixes, have noticed many without the slide stamped with a serial number in the traditional location. Searching through Gun Broker, have found some with barrels serial numbered, to frame, but no slide serial number, including a couple of "AF"s. Whether the slide was "replaced" at some time, of course is unknown.
The "dash" on your slide is an anomaly, the font doesn't "seem" correct, but as already recommended comparison to the frame is advised. It may have been "added" by whomever had done it, so it wouldn't be confused with factory applied number. Similar to what has been applied to the left side of some LE surplus. Have never seen Sig use a "dash" in serial numbers, but then again I've not seen them "all"!