Gustav Marzion's Signature

I'm still thinking that the signature on the board found in our old porch is Gustav Marzion (or Murzion, perhaps more likely). I found a reference to Emma Marzion in our own Smith-Zimmerman Museum site; she's buried in Graceland Cemetary here in Lake County, SD. She died in 1910. No Gustav, though; perhaps he moved on. A search for his name exactly, however, turns up nothing but this humble blogger's reference to him.

The name Marzion is common; Murzion, not so much. JB wants to know more about the signed S-L-K crossways on the board. Who's SLK? Gustav's more reticent partner? Every carpenter needs a partner.