Mullard valves boxes are familiar to folks. The NOS valves and the modern re-creations are in blue boxes with black /pink. The NOS ones will have a price on the box – typically “11/- + PT.” Yes this is the old shillings
The valves were also packed in red and black boxes during the 1960’s too. These boxes had no prices on them because they were destined for industrial customers and were sold by the Mullard Industrial Division
So they are not oddball fakes. Quite often the pins would be gold plated on the “professional versions”.
With each valve came a warranty leaflet. Back in the heyday of Mullard making valves in the UK, the warranty on rectifiers and double triodes was 3 months. If you kept the valve on the shelf in ints box the warranty expired after two years.
Each industrial valve came with a warranty sheet. Below are front page of the warranty sheet and the second picture shows the warranty period for each type of valve. The first section ” Receiving Valves” are the ones of interest to us audio amplifier users. It is old technology and while it sounds great is prone to failure due to all the heat used
But we just love how they sound !!
Today major amp makers still give a 3 month warranty on the valves but three years on the amp itself. We give a 120 day warranty on all the valves we sell