Your 545D, DD5PW2 is the model code and DD designates 545, 8x8 with PTO, not 445 which would be a KD designation, is about 1999-2000 judging by the serial number. The number is at the top range for the D series.
The date code is the third set of numbers/letters also found on the ledge behind the starter. It will look like 0F25B where 0=2000, 9=1999, etc. for the year. The next letter indicates month. A=Jan, B=Feb, etc. I is skipped and M is Dec. The two numbers after are the day and the last letter, usually B, indicating day shift.
The 545D has a 201 cid diesel with headland pistons and 10 more Hp than the 445D. The 545 lifts 5,000 lb., while the 445 lifts 4,000 lb. The lift cylinders and bucket cylinders are larger on the 545. Beyond that, they are pretty much identical.
