so is that frame useless .
Well...yep, depending on how resourceful/risk-averse the buyer. In other words, I wouldn't want to risk it, but someone might get away with riding this for quite awhile. The joint is largely under compression.
If they could have stopped before hacksawing the brass, it would have been better, but evenso...the crack is right between the stays. If the bike had used a side-stay attachment instead of a fastback, it might have been possible to drill a new crack-stop hole and extend the compression kerf down to it. In that case, all would likely have been well.
In this case...assuming the seat collar and tube top have not been distorted, much will depend on how the seatpost fits and whether the crack propagates further downward when it is clamped. A stop-crack hole would still be a good idea, but it will be hard to drill one large enough to dissipate the stress.
With this beautifully fillet-brazed frame and light tubing, it isn't as if there's a seat lug there for reinforcement. Unbrazing the joint and slipping on a seat lug would be more costly than worth it and risky as well; I'd be concerned about that much more heat in the tube ends.
A bit hard to tell from these photos, but it appears the seat clamp "ears" aren't parallel.
There's some story behind this. Fairly presented, though.
Best,
Dan.
