Every series has years where there are so many varieties to be found that it's worth examining every coin you encounter for that date/mint. For Roosevelt dimes, 1946 is one of those years, where each mint produced a number of DDOs, DDRs, RPMs, and other variety types. Among these are a number of multiple-varieties, where more than one variety can be found on a single coin.
I purchased this 1946-S at the Austin Airport show yesterday. It not only has a nice S/S RPM (RPM-003), but also a doubled die obverse (DDO-010), showing on the date, motto, and designer's initials. It's not a high-dollar variety, and the DDO isn't the strongest you can find, but if you enjoy hunting varieties, I encourage you to pay attention to those 1946 Roosies!