The P228 was originally developed as a more compact version of the P226, and was adopted by the United States army. The P228 later developed into the P229, and the two guns are one and the same only with the P229 slide built out of stainless steel in contrast to the P228’s carbon. This was done so the P229 could handle the higher pressures of the hotter .40 S&W and .357 SIG rounds. The .357 SIG version of the P229 serves as the main sidearm of the United States Secret Service, and earlier the P228 in 9mm served as their main sidearm.
The P228 was technically discontinued, but the same gun in the form of the SIG Sauer M11-A1 is still being made today. For all intents and purposes, the M11 is identical to the original P228, with only the markings being different. The M11-A1 is so named because it was the designation giving to the handgun by the United States military.