ID on tuba & adding a 5th valve

[tubbytubes]

Hello, I recently acquired this tuba, and I am wondering what the make of the horn its very old, most likely in F, and I want to see how hard it would be to add a 5th rotor to it I already have parts off an old Cerveny 681 and various other tubas, would it be worth:

1. replacing the lead pipe cutting it if needed to length and adding the 5th valve above the 1st valve rotor.
2. cut the stock lead pipe to fit and add the rotor at the same spot above the 1st valve.
3. add it bellow near the main tuning slide.
also what is a good length to have the 5th rotor a major 3rd configureation or a whole step?, i plan to give the horn a overhaul aswell adding new rotors and a new bel and a good clean.
I want to use this horn as a project horn/starter F tuba.
pictures:
https://drive.google.com/drive/folders/ ... sp=sharing

[arpthark]

With the very long lead pipe and tall top bow, I wonder if it might actually be in Eb. Hard to tell without playing it.

A Cerveny 681 rotor would probably fit better after the valve block, but it really depends on the bore. You may find that it won’t work in any logical spot and then have to find another rotor. Ask me how I know!

[tubbytubes]

Yeah i could be, the seller didnt have much info on the tuba and said
could be in eb or f , the only reason i think its in f the build reminds me of a B&S model 90 F tuba and the 2nd valve looks pretty short for an eb tuba , but truthfully in either f or eb i hope the horn plays well and is not in low pitch and having to do some cutting to get it to pitch , and to hopefully find more info on the make of this tuba see if i need a lower bore rotor or if its possible with what i got to add a 5th valve thanks for the insight!