Mullard used the Philips code system on their tubes. The first 3 digits of the code, usually found on the lower part of the glass and very hard to see, are of little consequence. The 4th digit, often beginning right under the first 3, will designate the Philips factory that produced the tube. The "B" indicates the tube was made in the Blackburn factory and is a genuine Mullard, regardless of what the label says. The last 2 digits will indicate the year and month...sometimes another digit indicating the week that the tube was made.
The Telefunken tubes are more linear, pure and focused. The Mullards more warm, thick and texturally harmonic. If I were after all my gear could take, I would go with Telefunken. If I wanted to add a liitle more syrup and give up a little extension, I would go with Mullard.
I hope that helps a little. Personally, I like the reissue Tung-Sol so much I would never spend the extra money on a NOS Tele as they command silly money. Valvos, if the price is reasonable will get you most of the Telefunken sonics for a fraction of the cost.
