Info lifted from the US site:

The diff has a metal dog tag on which is a code:

S409B
3L73 102 8C11

The break down of these codes:

S409B: S = Sterling Differential 409 = Print Number (Model Number)

B = Revision Identifier (Change in Design)

3L73: 3L73 = 3.73 Ratio L = Limited Slip Absence of L = Open Differential.

102 denotes the ring gear size. 10.25 inches. 105 would be a 10.5 inch ring gear.

8C11 is the build date.

8 = year of manufacture. In this case it means 1998.
C = month of manufacture. A= January, L= December so C= March
11 = day of manufacture. So My differential was manufactured on March 11, 1998


My Aussie F205 diesel truck has:
V431 F L73 105 4J29

What does the V mean? Not a Sterling diff ? 431 = print number F=revision
I take is the L73 means 3.73 ratio limited slip diff
105 for the ring gear
4J29 means manufactured 2004, October, 29th.

If you want to figure out whether an after market diff cover will fit you will need to check the code of your diffs. Can others please post their diff code for comparisons?