Bell's Royal Reserve

Hello, as I was cleaning out my recently deceased grandmother's house, I came across a bottle of Bell's Royal Reserve 20yr 43% blended scotch with a black label. The bottle was of the same fashion as the earlier Bell's rectangular bottles, except it had a Black label. I have been searching the internet looking for a matching bottle/label, but I could only find the white labeled bottles. Does anyone know the approximate year this was purchased? Thank you for the time.