Back on 15 May 2009 I posted my 1967 Papermate Ops n Pops collection. At the time I had six with the goal of ten. I now have number seven. The yellow one on the right with black squares. These pens are number two on my all time favorite pen list and as I said before it "is the 60s". This new yellow one has not seen the day of light for 40 years. I just put in a new refill and it works fine. One should be in your collection. Three more to go.