(under subclass 475) Subject matter wherein the means to hold the shutter open is provided by a member with one or more protuberances or grooves which interengage and cooperate with mating protuberances on, or grooves in, another member to form therewith a positive force means.
SEE OR SEARCH THIS CLASS, SUBCLASS:
, FOR 899, for a foreign art collection involving a pivoting or rotating blade shutter having a gear retard means.
