I have recently come into the posession of some old family slides. These slides are on 2"x2" slides. Trouble is, there is no projector. The box that currently holds these cak shaped trays full of 100 slides, shows this particular tray as a side loaded variety. MY QUESTION IS: DO I HAVE TO USE THAT PARTICULAR BRAND OR CAN I SWITCH TO THE CAROUSEL STYLE? mY TRAYS ARE gaf sAWYER bRAND AND I THINK THAT THEY ARE ABOUT 40 YEARS OLD