I have a Suntour freewheel (6 spd, "Perfect" model) that has unequal spacer widths. The spacer between the top and bottom 3 speeds is wider than the other 4 spacers. I purchased the bike used ('80-'81 Colnago Super), and I know the wheels (hubs and rims) are not original, but the freewheel (the body anyways) is of the correct time period. I noticed that the cogs do not have beveled teeth; I thought all SunTour FWs of that era had bevelled teeth to help transitioning from higher to lower gears. Teeth on cogs (excepting the smallest) have little or no wear (front 52T ring is unworn,44T ring shows wear); I assume previous owner rode the small ring in both the front and rear, rarely shifting. Bike is in excellent condition for 40 years old.
Freewheels normally had uneven spacing between gears back back then. Until indexed shifting became popular starting in the mid-80s, there was no need for spacing to be consistent. The outer sprockets were threaded on, and the inner ones were splined, so they weren't even attached in the same way. (Aside: I recall a bike shop had threaded together a "9-speed" freewheel and stuck it in their display case as a joke—It was much too wide to mount on a bike. Simpler times.)
I don't remember sprockets having fancy tooth profiles back then: that's an an even newer development to improve shifting.