67mm should also be stenciled on the front edge of the lens somewhere. If so, then you should be good to go. It should be on the lens because a lens cap can be lost or broken. 

Unfortunately this is for adapting lenses to Olympus' modern digital Micro 4/3 cameras. It won't work with the Pen FT or similar half-frame film cameras, and you most likely won't find anyone making adapters for these. 

For this series, front thread diameter is bigger than the back thread diameter.
for example:
Back thread diameter (attach to lens): 40.5mm
Front thread diameter (attach additional filter/other accessories): 43mm
Variable ND filter size other accessories size

37mm	40.5mm
40.5mm	43mm
43mm	46mm
46mm	49mm
49mm	52mm
52mm	55mm
55mm	58mm
58mm	62mm
62mm	67mm
67mm	72mm
72mm	77mm
77mm	82mm
82mm	86mm

 

This filter will fit any lens with a 49mm filter thread 

For this series, front thread diameter is bigger than the back thread diameter. for example: Back thread diameter (attach to lens): 40.5mm Front thread diameter (attach additional filter/other accessories): 43mm ND FILTER size front thread 37mm 40.5mm 40.5mm 43mm 43mm 46mm 46mm 49mm 49mm 52mm 52mm 55mm 55mm 58mm 58mm 62mm 62mm 67mm 67mm 72mm 72mm 77mm 77mm 82mm 82mm 86mm