Mastjack / Mast Step

I recently purchased a DS1. I really have no idea what year it is, hut it was advertised as a 1975, but I have my doubts. According to what I have read in this forum production had moved on to the DS2 by 1975?
My main question at this point is about the mast step. The manual available from the association website talked about a mastjack. I think I have just a plate, not a mastjack. I have included a picture, unfortunately it's after raising the mast. The issue I have is that I was not given a pin or anything that goes through the mast and the plate on the floor of hull. Does anyone know if I need a pin or bolt to hold the mast down?
Thanks in advance for any advice.
My main question at this point is about the mast step. The manual available from the association website talked about a mastjack. I think I have just a plate, not a mastjack. I have included a picture, unfortunately it's after raising the mast. The issue I have is that I was not given a pin or anything that goes through the mast and the plate on the floor of hull. Does anyone know if I need a pin or bolt to hold the mast down?
Thanks in advance for any advice.