is this a back pack tuba?

[sousaphone68]

http://www.ebay.ie/itm/Alte-TUBA-Horn-D ... 1c24892846" target="_blank" target="_blank
or just a small tuba or big euphonium

[Bob Kolada]

I say a small F (Eb?).

[Lingon]

...or just a small tuba or big euphonium...

The listing says height 79 cm (31 in) and length, open horn, approx 4 m which translates to about 13 ft. Small tuba in Eb?
Would be interesting to know who made it, and when...

[eupher61]

F tubas/horns are about 12' 9", give or take for bore and flare, so I'd say F.

[Gus_Pratt]

I vote F tuba, that the tuning slide has been modified to play in Eb.

[sousaphone68]

I vote F tuba, that the tuning slide has been modified to play in Eb.

After reading this post and looking at the photo again I think you are correct as it is very similar to the eb slide for the travel tuba.