Hello there. In this post I have a few Thorn Fluorescent tubes with unusual date codes. I am not very familiar with Thorn date codes. I believe that the 20W U-bend tube was manufactured in March 1988 and the 6W T5 tube was manufactured in January 1986 however I have no idea when the 13W T5 tubes were manufactured. Can anyone help me date these lamps. Thanks.

These do all have the standard Thorn date code.  You can find the details of the system on my website at http://www.lamptech.co.uk/Documents/Codes/Date%20Code%20-%20Thorn%20-%20Fluorescent%2015-Dot.pdf