My house was built in 1928 (in Altadena, CA). My detached garage looks like the same vintage, but I don't know for sure. On at least 2 of the garage walls, there are shims between the sill/mud plate and most of the studs. Many of these shims are not actually supporting weight--they can be shifted by hand. A lot of the structure seems to be held up by stucco, or something.
Why would this be? Does it mean that the foundation (concrete block walls) was added as a retrofit?