Yes, an interesting rifle. The body side wall T is smaller than the norm, but is of the same style. I have seen several of these rifles over the years (& own one), all of them being 43 BSA's.
Incidentally, what are the letters marked onto the inside of the body side-wall by the front pad screws?
You may also find it has the BSA examiner's stamp on it but not the D6E - but this is common on earlier rifles.
Nice find.