220 Long Rifle to .22LR

[ovenpaa]

Can anyone tell me when BSA stopped marking rifle barrels 220 Long Rifle and moved to marking them as the .22LR?

I am looking at the Model 12 marked as the former and I am just trying to get a view of when it was built. It has the wider actions so is indeed the Model 12 and is fitted with the BSA No 8 rear sight without detent and the windage and elevation screws have round heads with small relief's presumably to give a batter feel. The front sight is a BSA No 19 with the little lever to swap from post to ring and is hooded. 29" barrel.