Glass says 4 A6 then G. Black base says Super Silvertone Made in U.S.A. and 87X Reads 13.8 when I set it on 200 ohms on my multimeter.Can't tell you anymore. Got left these by my father when he died and I am liquidating his tubes. He was a ham enthusiast and fixer upper buyer/seller. Just going by pricing I see online, make me an offer. Anything I can do to check them out let me know. I have limited tools: a multimeter if that helps. All items "as is".I ship via UPS and USPS Ground. Alaska, Hawaii, and Canadian customers pay the difference between ground shipping to the nearest border and the cost to your door. I can also ship Overnight, Second Day, or Three Day at additional expense.Canadian customers may be subject to additional tariffs, check with your local UPS service.Payment is through PayPal.I am happy to help you with the items for sale. If you have any questions, please email and I would be happy to help. Please note that I will respond as quickly as possible.If you are inquiring about shipping status, tracking numbers, payment clearance, etc. PLEASE INCLUDE YOUR NAME, ADDRESS, AND eCRATER ID in all correspondence. Please supply this info and I can respond much more quickly. Thanks for looking!!Check out my other items!Returns for incorrect items only. All purchases are final unless items are not the item purchased. No buyers remorse returns accepted. If you feel an item received is incorrect, please email me within 48 hours of receipt.If an item is returned as incorrect it will be replaced with the correct item as soon as possible, once the mis-shipped item has been returned. No additional shipping expense will be charged.Please contact me immediately should you feel your item is incorrectly shipped. Regardless of the fact that I am listed as NOT accepting returns,items may occasionally be returned, exchanged, and/or replaced depending on reason.I try to be fair as I have limited testing equipment.NO returns accepted for buyer's remorse or change of mind! It's too complicated & costly. Please be sure you want the item.Thanks Again!!!Powered by eCRATER . List your items fast and easy and manage your active items.