Difference in Model Numbers?

I found some surplus gear and was wanting to know what the difference between C058900A122A and C058900P122A.

We just put up a few sectors of ePMP and got the C058900P122A from our dealer.  The surplus is C058900A122A.

Thought I would ask before I order the wrong thing.

There is no difference between the two. C058900A122A is the part number and C058900P122A is the model number. The label on the radio should have both of these listed.