Philip Stein confirmed they did make Teslar watches with rubber bands.  The only color they currently offer is black and this type of band is not listed in the collection on the website.    Also, they did make watches prior to 2005 that did not have serial numbers, so not all authentic PST watches have serial numbers but this will at least confirm while the watch may be unused, it was not manufacturered recently.  Also, watch out for unauthorized dealers.  If you purchase a watch from anyone unauthorized to sell them, you cannot get warranty service.  The warranty will be null and void.  Note, I got all of this info direct from Philip Stein headquarters via email so I can only assume it is accurate.