Václav Krátkoruký, Královské Vinohrady, Prague
Královské Vinohrady is a district of Prague.
An account of postcard activity around Prague is online
here
The small logo (MYK) on the address side of two of the cards is perhaps a printer's mark.
VKKV 258-2
VKKV 341-2. In Venice (?)
VKKV 1036