[AMRadio] Tube Question

[rbethman]

All,

I have two AN/URR13As.  They have a LOT of tubes marked 5003.

    1)  Is there a known substitute for this tube?

    2)  I have a Hickok KS-15560-L1 Tube Tester.  Are there updates to the
tube listing "chart" for this tester?

Thanks in advance.

Bob - N0DGN