There must be SA barrels from more than one source then. Many years ago Charnwood imported a load of them, all wax dipped, all with rear sight bases & all brand new (NOS) SA 1950's manufacture. When Charnwood ceased trading most or possibly even all of the barrels were bought by Terry Abrams. I managed to persuade Terry to let me have a few. I think he still has some, although last I heard he didn't have many left & so was reluctant to part with any more.