Still another object of the invention is to provide a focus transparency which can be stored in a protector and whose image is that of a test pattern useable in {HEAD ~ conjunction} with {TAIL ~ a registration device} for centering and focusing of the overhead optical projector before beginning a presentation of visual aid transparencies 
with
Still another object of the invention is to provide a focus transparency which can be stored in a protector and whose image is that of a test pattern useable in { HEAD ~ conjunction } with { TAIL ~ a registration device } for centering and focusing of the overhead optical projector before beginning a presentation of visual aid transparencies
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH