Circa 1903 with solid red band under cab, brass brake with outside rod, six boiler bands with 6-spoke drivers and solid tin pilot wheels. The example below came from the original owner - the tender has cast iron wheels and came with a single Princess car that also had cast iron wheels and the longer early couplers.

Circa 1904-05: same as above except two red lines under 3 cab windows. The 6 band engine above has no coupler on the front truck, no reverse lever and silver trim on top so it is probably a No. 20. The locomotive below has a coupler a coupler on the front truck, a reverse lever and gold trim it is probably a No. 25. It's always hard to differentiate as couplers fall off, trucks get replaced and the reversing lever can fall out. If you actually get a working 25, the key will wind the other direction when the reverse lever is activated.

Close up of cab and 'reversing lever' protruding from cab.

Later 6 band with correct early tender.

Very late 6 band No. 25. Same as the one above, but new motor with inside brake.

This appears to be another early No. 25, but note that this one has no reverse making it a No. 20, note also the straight brake rods.