Chang's twin's, 4 letters
Locomotives, 4 letters
Locomotives: Abbr, 4 letters
M.I.T. grads, 4 letters
M.I.T. grads: Abbr., 4 letters
Machines: Abbr., 4 letters
Many BS holders, 4 letters
Many Caltech grads: Abbr., 4 letters
Many M.I.T. grads, 4 letters
Physics pros, often: abbr., 4 letters
Road designers, e.g.: Abbr., 4 letters
Some B.S. holders, 4 letters
Some M.I.T. grads, 4 letters
Some M.I.T. grads: Abbr., 4 letters
Some MIT grads, briefly, 4 letters
Some R.P.I. grads, 4 letters
Some specialize in elec., 4 letters