) I did some searching here on the forum, and there's not a lot of detail about the 1050, which might be just as well because they aren't easy to find. Some people expressed a preference for the newer Getzen 3508 dual bore 500/508. Everyone seems to like the 1050, but there isn't a lot of detail. The most interesting fact was that the slide is compatible with the 6h family. Getting a 508 48h would really be something.
I'm using a DE xt104D3O with a slightly undersized Olds shank taper on both instruments.
Anyway, for reference I'll characterize the 48h the 1050, and then combinations of bells and slides. To me the 48h is kind of characterized by it being one of the trombones the Air Force band bought in quantity in the late 50s. I can only imagine these were great marching instruments. Not to be disparaging, but the instrument is loud without being shrill, and clear without being bright. Also, they are slightly more ergonomic with the gusseted braces. More strident than a 6h due to the bell (nickel plated yellow brass, although there is some speculation some were Coprion under the plating). To me, they play on the dark side, but balancing on the edge crass if you push them too hard. It requires some control to keep the dark tone without creeping into crass edginess. These are pretty well known horns.
The 1050 comparatively is a little more free blowing, probably due to 500 vs 508. It has a nice character to the sound, but doesn't have the dark quality you can get from the 48h. The 1050 is considerably lighter in both halves than the 48h. It plays nice. Not as dark as the 48h, but also easier to keep out of the nasty sound that you can fall into with 48h. This could just be my chops showing their preference for slightly larger bores.
48h slide = 507g
48h slide width (inside to inside) = 2.74"
48h bell = 912g
1050 slide = 478g
1050 slide width = 2.75"
1050 bell = 772g
Combining the 1050 slide with the 48h bell was really what I was after here. The sound retains the dark quality of the 48h and gains the easy blowing nature of the 1050. It might be a little harder blow up high (high Bb), but up even higher (high Bb-F), it rings. I think this is a combination you might get away with on some legit situations if you can control (tone down) articulations. Certainly an upper part in trombone quartet, and I may try it in quintet, although a trigger is useful there.
The 48h slide with the 1050 bell had a nice sound, but it wasn't as remarkable. The high range seems to have a slightly covered feel in comparison, and the super high F (top line treble staff) doesn't ring the way the other combination does.
I'd also have to compare this against my Olds Recording. The Recording has a nice sound, but it's more of a mellow ballad sound than a clear ringing powerful lead bone sound. The same would have to go for comparisons against my 32h and Yamaha 455.
Anyway, never pick a horn based on specs, and certainly not a single measurement. The dimensions give you clues you can use to start a search for a sound, but materials, construction, tapers, radius values (and some things you can't see like material condition and heat treatment) combine many factors to create the sound.