DELL PR01X Port Replicator D/APR Laptop Docking Station

No.  The 1520 doesn't have a dock connector - you can use a generic port replicator (USB or Express Card) but there's no provision for a true docking station with this model (or any other current Inspiron).

Dell Port Replicators only with with Latitudes, Precisions, and the XPS M1710 (strange, but true).

No.  The M4600 need the newer E-port, not the old D-port.

Is it compatible with the Dell Precision M4600? Thank you for the information.

Aha. Thank you. What about Latitude E6220?

All E-series systems (and Precisions based on them -- meaning all current Latitude and Precision models) use E-series docks.

The last ones to use the old D-docks were the Latitude D830, D630 and Precision M90.