The rarest T-Type by a very wide margin: just 379 built in 1939 before the war stopped everything. If you find one for sale, the question is rarely “is it good?” but “is it real, and can I afford it?”
What you're buying
The TB introduced the XPAG engine — 1,250 cc, twin SUs, 54 bhp at 5,200 rpm — along with a dry-plate clutch replacing the TA's oil-immersed unit and revised gear ratios. It was available as an open two-seater or the more luxurious Tickford drophead coupé. It is narrower than the TC that followed.
Then Abingdon turned to bomber cockpits and Matilda tanks, and the TB was over after 379 cars.
This is a collector's car, not a starter classic. Its rarity dominates every other consideration.
Verify before anything else
With numbers this small and TA/TB bodies looking near-identical to a casual eye, provenance is everything. Check the chassis number on the left-hand front dumb-iron, check the XPAG prefix on the engine, and obtain the factory production record from the T Register before you go further. Confirm what you are actually looking at.
Condition and parts
Mechanically it is an XPAG car, so the engine notes for the TC apply — including the weak original crankshaft. Structurally the ash frame rules apply as they do to every T-Type, and with a TB the cost of getting it wrong is higher than the cost of getting it right on anything else. Pre-war T-Types are very rare outside the UK, so many parts will be sourced from Britain, and TB-specific items are scarce.
Who it suits
A collector who values rarity and the XPAG's introduction, and who understands they are buying into a very small club with a very small parts supply.