Both the vintage USA and European versions of this tube are excellent. These resemble airplane wings with a rounded front edge and a tapered opposite side where the plate is joined by a rivet or weld, and the two plates point in opposite directions. The only difference is in the RCA 12AT7WA military versions, where the plates look like tiny 12AX7 rectangular plates. All I have seen have the wing shaped plates. All seem to be top getters, with either a square or D shaped top getter.
Some tubes have both type numbers on the label.
These usually have thick mica spacers. This tube is usually very low in microphonics due to it's rugged construction. It most likely is because it has a lower gain, a mu of 47 compared to 60 of a 12AT7. These tubes are still plentiful, and are really well made. It maintains it's output even if the filament voltage varies.