Re: Mechanical difference between K-37 and K-36 question

What this all boils down to is that the only sure way to determine if a locomotive is superheated is to look into the smoke box. There are a few general rules, though there exceptions to all of them:

If a locomotive has a front end throttle it is most likely superheated. This is easily determined only if the throttle linkage is outside of the boiler, which was not always the case.

As noted, a damper in the smoke box usually indicates a superheater, but again this was not always done. The visible evidence is a lever and counterbalance on the smoke box side.

Slide valves were problematic with superheat and nearly all locomotives built or rebuilt that way were quickly converted to piston valves. The major exception was Lima, which continued to build superheated Shays with slide valves for several years after the other builders had switched to piston valves.

The pattern of five bolts on the sides of the smoke box, for attaching the header, was not evident on earlier superheated locomotives, nor on lokeys that were converted. For instance, the Northern Pacific ordered superheaters on all locomotives built after 1910 and converted many others, but the bolts did not appear untill 1920.

Some superheated Mallet compounds had slide valves on the front engine. The thinking was that much of the heat was lost by the time the steam reached the low pressure cylinders, and if the engineer forgot to open the cylinder cocks the pressure would lift the valves off their seat rather than blowing a cylinder head.