I'm interested also. I heard a guy from Siemens once mention the existence of a "TK" version of the soft start logic board. Then the parts folks in my company acted like I was an imbecile when I ordered a logic board for a Siemens soft start a couple years ago and noted it was specifically for a TK. But I find it odd the guy from Siemens talked like it was different.
As far as I know though there is no real difference.
Waiting to see any good info here