[tarh331Dad]

Does anyone recognize this Roller-Key-Cluster?

The horn was built in Elkhart, but it doesn't look like any Buescher I've ever seen, and I can't find any pictures of original Martin sopranos.

Another possibility would be that it's a [rather rare] original Elkhart Band instrument, from the period 1923-1926, before the merger with Buescher in 1927.

 

[lostcircuits]

This one is slightly older (ca.1915) but maybe it helps

 

[tarh331Dad]

What do you make of that crazy-weird forked thingamabob on the G# key?

Could that have been an aftermarket add-on?

I've never seen anything quite like that.

 

[milandro]

are you sure that this is not a perspective "trick or the eye”?

 

[PigSquealer]

I can't find any pictures of original Martin sopranos.

If it's anything MARTIN you'll find it here.
http://www.themartinstory.net/version7/index.php