I just opened a case of new old stock lamps, the date code on the box is the 23rd of September 1997 - I know I forgot about them in my lamp cabinet and they got pushed to the back. When I took one out of its box to install it I notied a small amount of brown discolouration in the gas and the quartz envelope was not as clear in the filament region as normal. I checked all twelve lamps and saw the same thing. The box of twelve had never been opened still taped shut with the manufacturr's original tape. I have sent an email to the manufacturer providing all the detailed information from the cade label. This is why I didn't mention the name. these are the HPL575/115 version of the lamp. Has anyone else seen this before? I cannot take the lamps back to the supplier because they are no longer in business. Also I know I clearly keep far too many lamps when I can have a case of twelve get hidden like this.