The folks I bought my A100 from purchased it from the original owner in the hopes they could chop it. I guess they didn't realize an A chassis isn't good for that mainly because the pre-amp sits under the tone generator as opposed to behind it in the B and C chassis. I haven't ever measured the width, but I can see how the A100 might be narrower due to the thickness of the wood sides on the B3.
I believe DocJohn was referring to the original model ''A" (mid 1930's), and not the A-100 series. The model, A is shaped just like a B-3, except, like Doc mentioned is a few inches more narrow. Those organs are so old, that there are not many around(but I happened to play one just a few days ago.
I've owned at one time or another, most of the consoles and tube leslies that hammond made...Including the model A, and as mentioned there are so many factors that change the color of tone, that each one does have a unique sound. Old timers will tell you that CV/BV are actually the best sounding hammonds, but it just doesnt have the flexibility with percussion and all. I do have two B3's that I use for recording in the , but we do also have a B2(unmodified so it has ratchets) and it is a great sounding organ. I live closer to St Louis, than Chicago, but I've talked to old hammond dealers in Chicago, and many of them consider the B3000(a glorified model H) the console the ruined Hammond.
By the way, when I was a hammond hunter, God gave me great favor, I've owned over 40 or so. ..I've purchased c-3's for $250, and leslie for $75, and I turned down A-100's. The most we ever paid was $1,000, and that was for a mint condition 1958 B3,tone cabinet, and leslie. That was the one and only time we ever paid a grand for a hammond. Now I just have the (2) B3's, a B2, and a m2
**the worse thing you can do, is not play a hammond...secondarily, is to not oil, or overoil, out of all that I've owned, I never put a trek unit, or transistor amp..some of them organs 70 years old, and still playing strong