Hello and welcome!. We tend to use the SA hub stamp to date our 3 speeds. Unlike motorcycles, there is no official model year designation for these bikes. There is a general chronology of changes over the years that can pin down a reasonably close date of manufacture, put this image is far too small to see the details needed. More than likely, this bike has a Sturmey Archer AW hub. These are amazingly reliable units so problems shifting are usually cable adjustment or some other simple fix.