Been reading up on old racing practices and came across this statement that raised my eyebrows and am hoping someone can further explain: "Front dampers have a slight damping effect on bump (about one third of that on rebound), whereas rear dampers have damping only on rebound. Adjustable dampers, as fitted on current racing and sports/racing cars, enable a fine balance to be obtained between suspension bounce (when the wheel can be observed, and felt, to be working too freely) and a harsh ride, with too much shock being transmitted to the chassis and with the suspension working out of phase." Michael Costin and David Phipps, Racing and Sports Car Chassis Design, 1962, pg 64-65 So essentially they're relying only on friction for slow rear bounce (bump) damping?
Sounds like it, at least in that author's philosophy. Then again, looking at the spring rates being used at the time, you wouldn't really need much compression damping.
Costin was co-founder of Cosworth after working at Lotus and Phipps was a photo-journalist hanging around motorsports.
