The two sb MP distributors I have had both had 24 degrees of advance in the plate but one had two pink (lightest) springs and the other had one brown (the next one up from pink) and a two stage sping with the oblong loop.

The one I mentioned above was adjusted to 16 degrees of mechanical with tow brown springs. This has the advance all in at 2600 rpm and combined with the 17 intial gives me 33 total mechanical.

With the 17 in the vacuum pod I can have as much as 50 degrees at light throttle cruise.