This was going to be a thread about a Heathkit RF Signal Generator left in my garage by the previous owner. Is it useful, that sort of thing. Being an unapologetic tinkerer, I had to open it up. And looking up at me are the words....IEC Mullard! Woo hoo. One 12AT7 and a 6AN8A. GT BRITAIN IEC Mullard (Next to each other, not on top of each other) 1022-940 VF3 88K4 or 58K4 or B8K4 Cant quite make out the first character. Anyone know a good reference site for Mullard dating, etc.? Thanks!