Canon liked to sell cameras at several price and feature levels. In particular, they were good at taking a base model, removing some features, and selling it as a "value-priced" alternative.
In this case, they took an FT, removed the self-timer and lowered the top shutter speed to 1/500th. It was purely for the export market (Europe and the US).
Later on, when they revised the bodies to use their FD mount, this became the TLb.
For more information: Canon Camera Museum