I picked up a Leitz circular polarising filter that was labelled as a 49mm filter on the case, but on trying it with my lens it doesn't seem to be a 49mm filter (i.e. it doesn't fit my lens). The filter has Leitz Wetzlar Germany P-cir 13354 on it, any help with figuring out what it is and what it fits? I'm admittedly new to filters and all that so all I know is it's a circular polarising filter. Thanks!