Questions about a Vintage Alexander Mainz Trombone

[hashkz]

Hello,
I’m looking for detailed information about this trombone.

It is made by Alexander Mainz, and I believe it was manufactured around the 1970s. I think the long water key was added later.
If you know anything about it, I’d appreciate your input.

[SamBTbrn]

That doesn't look like any Alexander trombone I've ever seen before... I would say it's a very customized trombone with an Alexander bell?

[Leanit]

Fat man's horn.