Mechanical or hand rung bells?

I have been wondering about what type of bells the D&RGW (narrow gauge) locomotives used. Mechanical or hand rung.

Hand rung seems the obvious choice, but then in some films I have (1960s K-36) the audio sounds like a mechanical bell. The sounds are probably dubbed in and not original, but then again I'm not sure.

But to me, the bells you hear in Durango nowadays sure sound like mechanical bells. And I was obviously too excited to even pay attention what kind of bell was used when I had a cab ride in #486 two years ago.

Our model train layout is set in the late 1940s to very early 1950s. Does anyone know what type of bell the following locomotives had in this time period?

K-27 #461 (Rio Grande Southern)

K-28 #473

K-36 #489

The sound system we use has the option of either bell. So it would be neat to get the right one for the right loco, if possible.

Matt
Lake Forest, CA
Click Here for my model train photo website