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I recently restored a 1906 version of the same horn. Mine was low pitch so in some ways was easier. You have to answer the question, what do you want? if you want to play a little Eb, they have a big sound and are fun to play, but you may have to fabricate longer slides to make it play in tune. Are the valves any good? Do you want an F tuba. Well you can cut it, if you know what you are doing. Several here have done that with good results. This will not be less expensive than making a playable as an Eb. Add a valve, good idea and has been done. You are taking a risk, these sometimes do not work well tone wise and ergonomically. Use a modern valve set. Higher probability of having a great horn. More expensive and time consuming. Talk to a knowledgable tech who has experience. You likely will not get your money back from any of these options, you are doing it for yourself, so what do you what and what are you willing to pay?

Mike,
For what it's worth, those little Eb's in 1912 (and +/-) were known as model 30s (and were then renumbered to 640 HP, 641 H/LP)

They made a bunch of then because they were they were light and easy to carry, so you could march with one, carry it to/from gigs without much problem and had a good sit-down horn as well. Not to mention the Bb treble/Eb bass transposition trick worked great for bands and schools.

You should be able to compare the slide length of your good one to the one in pieces to see if the other one is either HP or H/LP. One of the two may be HP, but have markings on the slides to tell you how far to pull them out for Low Pitch. It was customary at that time to leave enough length slide length to pull out for Low Pitch if you needed to play that way. All you may have to do is use a tuner and pull the slides, even the tuning slide. Even if the tuning slide is too short, a "ladder"-type extension could be made for it, then you leave the original horn original; no harm/no foul.

Wade mentions the potential unreliability of an F conversion for the other, You need more valves and you still don't know what it's going to sound like or how the intonation will be. I'd be inclined to just get one Eb to 440...

For the sell as is, expect to average $200 for each horn. You may have to wait a while because there aren't a lot of folks looking of these horns as parts. If you fixed one up as a 3 valve Eb, you might get $500 or so. Cost depends on the work needed and as you can see, there are varied opinions on what is needed. The biggest cost would be a valve restoration. If you did that, you would not get your money back. Adding a 4th valve and the conversion to front action would likely cost $1000 to $2000 depending on who does it and the extent of the work. That does not include the valve set. I have no idea on the conversion to an F. In my opinion, adding a 4th, modifying with a new valve set, or turning it into an F is a labor of love. You would not get your money back when you try to sell it. It's like restoring old tractors, you put a lot of money into something you cherish. You never expect to get your money back.

Are these tuba available to buy?

Sent a pm