I just bought 2 of these about a week ago. One for my 78 elky and the other for my son's 2001 blazer. They are new take-offs. These are the later stlye with the flip up/down day/night adjustment rather than the older side to side lever. They are from late 90's GM trucks but mount to the standard windshield mount. They say 'Donnelly" on the back which is what my son's old one said. Hard to beat the price at $4 each! He ships fast too. I bought them on a Sunday and had them on Wednesday from Texas to NY.
http://cgi.ebay.com/ebaymotors/GM-TAHOE-SUBURBAN-YUKON-TRUCK-CAR-REAR-VIEW-MIRROR-10_W0QQitemZ350247935491QQcmdZViewItemQQptZMotors_ Car_Truck_Parts_Accessories?hash=item518c675e03&_trksid=p3911.c0.m14