I had the bottom box already. This weekend I purchased the middle and top box from a member on here. The top box had 4 repaints, one red repaint, one orange, one black, and one grey. Plans are to strip the top box and repaint it to match the other two.
What points you to the 60's on the bottom? The name plate looks the same on the middle and bottom box, and the codes on the back of the middle and bottom end in 74 & 76. Does that correspond to the dates of the box? I couldn't find a model code on the back of the top box.
The bottom is a between box, meaning it has the more modern badge of the 70s, but is built in 60's fashion. The drawer pulls (rounded vs the square of the 70's build style) are the giveaway.