In the tables of Baldwin locomotive data there are construction numbers and sequence numbers. These do not necessairly follow in correlative order. Can I get some opinions to explain how these numbers are assigned?

I believe that the builder's number is the sequential numbering of locomotives outshopped.
There is another "class" number that is sort of sequential that was also applied to steam locomotives.
For example:
I worked closely with 2 Baldwin 4-4-0s at Stone Mountain.
Former Red River & Gulf #104 is Baldwin construction number 52209, Aug 1919.
Its Class number is 8 24C 221.
These class numbers indicate the wheel arrangement and cylinder size and the number the particular locomotive represents of that class.
In this case 8 24C 221 = 8 wheel, 15" cyl, 4 coupled drivers and the 221st locomotive with that combination.

In the case of former San Antonio & Aransas Pass #60, Builder #55390, May 1922, it was 8 30C 700. (8 wh, 18" cyl, 4 coupled)
There were a couple of sisters and they received 8 30C 701, 8 30C 702, etc.
The next locomotive with the specs of 8 30C would be sequential after that.

I hope that helps

Kevin
CSX Atlanta Locomotive Shop