I have a pair of 2405 - 16 ohm drivers that have aftermarket 8 ohm diaphrams in them. I have obtained 2 - NOS JBL D16R2405 diaphragms from different sources. One was in a sealed JBL box and is gold in color. It is stamped "Jan 23 1996", "2405" and it has an "SP" inside a circle stamped on it as well. The second is in an older unsealed JBL box with a 1979 ship date on the box and it is blue in color. The second (blue) is stamped "APL 1979", "33752", "2731" and it too has an "SP" inside a circle stamped on it as well. Both the "33752" and "2731" are very very faint so I could be missreading the numbers. I measured ID, OD, and Voice Coil ID and they are identical to the 2nd decial place. The thicknesses vary with the older blue at ".370" and the newer gold one at ".350" which is the only difference I can see between them aside from the color and markings. Both measure within .1 or so of 7 ohms and both of them have a hand marked little dot/line by one of the VC leads which I assume identifies polarity. I use the 2405's in a home stereo and want them matched. I believe the gold colored one in the sealed JBL box is genuine but since the blue colored one was not in a sealed box I'm not so sure about that one. Can anyone offer any insight into these diaphagms? Which post (red or black) does the marked (dot/line) lead go to? Thanks for all your help.