The 238 and a Mustang Pocketlite (not Mustang +II Pocketlite) are almost 100% identical with the only changes being that the 238 has a different slide and safety profile, and that there is an added removale mainspring housing to make a full field strip easier.
Here's the Mustang (sorry about the poor pic, I'm looking for a better one. (Brownells and E-Gunparts only have the Gov't .380 schematic)
And here's the 238
Also, it looks as if Sig is incorporating a steel guide rod instead of the plastic rod found on the Mustangs and the rear of the grip is more blocky than that of the Mustang family, probably to better accommodate the removable MSH.