I have a data set with paygrades from 3 to 16. The difference between each pay grade was probably not exactly the same, but the differences are very unlikely to have been big. From a different dataset from the similar context there was around $6-$9 difference between one grade and the next. I don't have figures for what people were actually paid, and for this dataset I don't know exactly what each paygrade meant in money terms. Since this is historical data, there might not be any way to find out.
At first I used an ordinal regression with paygrade as an outcome variable, but it seems overly complex and hard for readers to interpret with the large number of intercepts, and I am wondering if I could treat them as a continuous variable and do a linear regression instead.