Thanks Paul..
A little embarrassed, as in the cold light of morning, I can see it says sachs IV/K!! :

My excuse is the lok has been heavily weathered / badly painted black (yes, it is that heavy!) so it is difficult to see the plates under all the paint!! ???
Does not help when the job-sheet says 2
1841 and calls it a Mallet..
Thanks to Mark also..
In other news:
Mark has also been very helpful in letting me pick his brain / bouncw ideas off-of-him, for kit he had not necessarily supplied.. As usual above and beyond Mark.
Many, many thanks!