[Elecraft] Difference between a K3 and a K3S

[Tom]

I wonder if I can upgrade my K3,  (Sn # 53, yes 53),  to the HRO-500 
concentric knob? Anyone done that?

And yes, I have expressed interest to Elecraft for the synth upgrade.

We (K8AJ and myself) will be buying a K4, but when it shows up, um, she 
gets primary use of it.

I'll be allowed to use the K3 and any leftover antennas. So I had better 
make the K3 the best I can.


Tom K8TB