2 cent tip

[BR60103]

Numbering your "many of one type of engine" over a range suggests that the railroad is larger than is shown. (Look at Thomas the Tank Engine: sequential numbers from 1 up, every engine different {with exception}, no pattern to tender vs tank engines.) A little variety in details suggests a line that has made improvements over the years, but hasn't managed complete uniformity. Most railroads managed a pattern to numbering with the first digits giving a class and the rest being roughly delivery sequence. (But I can give lots of counterexamples to the last.)