Polish censor in 1946?

Hi
on this card from Poland to Switzerland in March 1946, there is a circular mark "R.P. / U.C. / 3206". Is this a censor mark? if yes, from which organization?
best regards, Peter

on this card from Poland to Switzerland in March 1946, there is a circular mark "R.P. / U.C. / 3206". Is this a censor mark? if yes, from which organization?
best regards, Peter