Here comes a pic of the original filter:
It's size is around 10mm x 10mm x 1mm. The inner diameter of the ring is around 14,5mm.
Perhaps the filter available on ebay cuts too much visible red light?
T =50% @648+-15nm
I'll try to find a filter where the full transmission curve is available.
There is a second version of the filter (12 x 12 x 1 mm):