Does anyone have any info on what this is where it fits and what it's purpose is?

Yes. What would you like to know? >;-)

In general terms, this was a device that served to remotely open the valve of a steam locomotive (or other steam, such as a plant or tugboat) whistle with a pneumatic operator, instead of a cord/rod operating a valve lever at the whistle--much like, say, power-assisted auto brakes as opposed to pure brake-pedal car brakes. These were commonly used with Hancock whistles in high-pressure applications, to assist in opening the valves against pressures of 250-300 psi. (Viloco and Hancock apparently worked with one another.)

Let me guess--6069 has one.

Alexander.
Yes she has/did have one fitted. When the whisle was removed by as yet unknown persons, the Viloco valve was stashed away until I came across it recently. Interestingly 60 has had the setup where the whistle was operated by the valve or the old way of pulling on the cable.

As I mentioned to you in an earlier post, the CNR Hudsons were very similar to the Mountains. CNR Hudson #5700 (nee 5703), an hour away from you at the Elgin County Railway Museum, has the same dual setup for the whistle.

I wish I knew if someone had a manual for this old beast that tells you what went where....

We have a manual we made up for CNR 5700 a couple of years ago. One of our members used to fire 5700 back in the '50's. He was very helpful in telling us what went where and what it did. He was one of the last engineers on 6218's excursion trips in the late '60's. I'm sure he fired a few CNR Mountains in his career too.

The Viloco device sounds like the same appliance that PM 1225 has. It's a little squeeze handle next to the brakestand that admits air to a servo cylinder that actually opens the whistle steam valve. Very quick and easy to operate, but the whistle is always either open or shut - no way to modulate the opening of the whistle. We have modified the engine so that the whistle may be operated by a lever pulled by traditional rope, enabling lots more fun with the whistle.

There was another appliance, an automatic whistle blower, that would automatically blow a grade-crossing signal with a single actuation by the engineman. I have seen an advertisement for this, with grisly grade-crossing-crash photos, but have never heard of a surviving angine equipped with one.

The pneumatic whistle operator was known contemptuously as a "button whistle." I believe it was the late, great David P. Morgan who observed that it made "every engineer a Poor Johnny One Note" since the whistle operator removed the opportunity to quill the whistle.

The Canadian Pacific G-5's were so fitted, and I remember Dave Dunlap, who ran 1286 on the old Maryland & Pennsylvania RR out of York, Pa., grumbling about it.

Well we have the whistle operator, now we just need the whistle!