Ah Uhhm....I think you better do some research re Charly before trying to speak with him.
The 50s quad of Mullards I own all have small halo getters and Mullard type code etched in the glass. Try Tube Asylum it's easy to upload a picture and the fund of knowledge very broad indeed.
BTW If your tube was a 7591, an EL 84 variant,it would have a plastic base, however it is a bigger base than a wafer or coin base. The 7591 is not a direct sub, due to a different pinout,
The 50s quad of Mullards I own all have small halo getters and Mullard type code etched in the glass. Try Tube Asylum it's easy to upload a picture and the fund of knowledge very broad indeed.
BTW If your tube was a 7591, an EL 84 variant,it would have a plastic base, however it is a bigger base than a wafer or coin base. The 7591 is not a direct sub, due to a different pinout,