I was slapped in primary school, in the 80s, with rulers, pieces of wood from the edge of the blackboard, hands etc and I was a really quite, studious child and this was par for the course for wrong answers in homework, being accused of day dreaming etc
At home my mother had a REALLY short fuse and was a stressy, anxious short tempered parent. My dad worked a lot and never really hit me that I can remember, he excelled in the 'guilt' chat - 'you've really disappointed me etc' which I hated with a passion.
My mother hit me a lot, with her hands on bare legs or arms, very stingy & smarty. Or sometimes with the back of a hairbrush. Very hard. She used it as her no 1 go to method of discipline for my whole childhood until I hit my teens. My sister is much younger and she never hit her, which always felt v unfair to me. She took all all her frustrations out on me and it was a wider family 'joke' how quick she was to anger & how impatient with me she was (not that I ever found it funny)
The absolutely infuriating thing is, much like the OP, she totally re-invented herself once she became a grandmother to my dc who were the first grandchildren. She's positively earth mother now and would intervene if I spoke in a firm voice!
I have never once put a hand on my children in anger or frustration and they're now teens. And I never will, neither has dh, despite a very troubled upbringing. I am really proud of that. We were not a shouty family either , my mother was very shouty.
She seems to have whitewashed her own behaviour in her own head and has no recollection. But I have not forgotten. Nor will i.
There is literally no excuse worthy of hitting children imo