A Time/Life with less holes  

O.k. I got the photo up
Those glides are snaked off of a later chair. Any clues?
I found this "Lobby Chair" on the sidewalk a few years back.

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an improvement... I've seen this happen in another design where the manufacturers or designers realised at a later date that it is easier on the eye to have one screw and a concealed pin locking the seat/back in position to the frame rather than 2 screws.
Either that or a chair can be assembled with screws attaching the seat to the frame from the inside prior to the final upholstery work, like the latter Brnos.
I'm sure LRF could help with the dates.

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Yes, it has pins where the Allen bolts would be. If it was done as an improvement, or proto, it was a short lived experiment. They still make, at least, the executive chair version of this and it has the four holes on each vertical. I have seen pics of many years but not that I could tell were like this. Thanks

2 Versions
There are 2 different versions of what is commonly referred to as the "Time Life Chair" -- a desk version and a lounge version. I believe yours is the lounge version.
Usually, the lounge version (unlike the desk version) is not height adjustable; and it also may not have adjustable tilt -- not sure.

I am sitting as I type this...
I am sitting as I type this in a 1978 (the date is stamped on the base) desk version. It has adjustable seat, tilt and casters. It has six (6) screws holding the frame to the seat