Conn Marching Mellophone Mellophonium French Horn Needs repair!

Description

Conn Marching Mellophone Mellophonium French Horn Needs repair!
I believe it is clogged up with something, I cleaned out what appeared to be a mud wasp nest out of the opening, but still can't get any air through.
I really don't know much about musical instruments, it could be an easy fix or just need cleaning. It appears to be silver or silver plated, but not sure.
Has a few dents and dings, nothing to major. (see pics)
(I have removed the tape since taking the pics, there wasn't any damage or anything under it, don't know why it was there)
Please view pictures to see more detail on the condition of the item!
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