The 2 iron was 17 degrees. There was not a 1 iron T-MB. The U-510 has 16 (1) and 18 (2) degree options and the U-50 has a 17 (2) degree option. T-MB is discontinued for 2020. In the 1980 Tour line, the 1 iron was 18 degrees. Now that 2 irons have less loft than the former 1 irons, you won't see many made anymore. Other than the U series, the only Titleist iron with less loft than 21 degrees is the T300 at 20 degrees, but it is labeled a 4 iron.

Not sure if you can still get a hold of a T-MB, in fact I don't think there was a 1 iron, but the U-510 is available in a 1 iron.