Why sometimes I find Helvetica with the letter "a" with the right leg straight and other times I find it with the right leg turned to the right:
- Letter "a" with right leg straight:
- Letter "a" with right leg turned to the right:
The right leg is reduced for thicker weights, eg. bolds and blacks, probably as optical corrections. Basicly, the thicker the weight, the smaller the leg. Myfonts offers a live preview where you type in your own text and they set this up in all the weights, so you can easily see the difference.
Regular vs. black below (blue), then it gets proper straight for the Textbook weights (pink).