Quote from http://www.rolleiclub.com :
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The Rollei 35 S (The S stands for Sonnar lens) series consisted of two identical models; in silver and black.In Singapore, from September 1974 until February 1980, 260,000 of these cameras were made.
The black model production (with black coated aluminum covers) started mid 1976. Serial Numbers run from 6.500.000 to 6.799.999, thereafter the lens number was the serial number.The Introduction of this top-of-the-line model with the newly designed 2,8/40mm Sonnar lens (5 elements) was the reason to rename the original Rollei 35 with Tessar lens into Rollei 35 T.
Starting in 1977, feet and meter scales were printed next to each other on top of lens.
Camera weight 345 grams (brass covers), 325 grams aluminum covers. Size 97x32x60mm.
Camera price in `1976 was about DM 500 ($ 250).
Camera included the Rollei leatherette soft case, a lens cap, wrist strap and manual (silver cover). All packaged in a silver colored box.
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Introduction
I found this piece of history in Germany, made in Singapore however. It was in perfect working condition, which I shot a roll of film in Italy. I like it so much that I put in my waterproof backpack everywhere I go. Thinking that ‘analog cameras are fully mechanical and rugged’, I sit against my bag and the focus ring got stuck.
To fix it, I consulted some local repair shop that quoted me for ~$120, I decided to ask on http://www.rangefinderforum.com forum for help. Special thanks to moderator jonmanjiro who shared with me a hint how to open the lens. Here’s how:
The first step is a bit tricky. jonmanjiro mentioned to pry the ‘front plate with the serial number’ off with a toothpick in the grooves. The problem is I don’t find any grooves. I stick my fingernail to the outer diameter of the plate, wriggle a bit, to find any weak spot. With the same spot, I put a flat screw driver in to pry it off. Careful not to hurt the lens, or you may stick a piece of tissue paper on the lens element.
Next you will see 3 screws that holds the focusing ring, unscrew them. Picture shown here had one screw removed.
Simply use a lever to ‘unstuck’ the ring.
Hope this help!
Witono's Freestyle 
Hi,
Thanks for this post. I have a Rollei 35s very good condition except the focus ring which is totally stuck (can’t turn it at all). Can you explain me what should happen when you use a lever on the ring?
Thanks in advance,
Stephane
Dear Stephane,
I can’t find a good analogy/example to explain how it feels like (like pop a bottle cap or sth). The focus ring was stucked because it got pushed inside the wrong groove, so ring should pop back to the ‘normal’ position when you use the lever.
Hope that helps.
may I ask how you put the front plate back onto the lens? I tried and it wouldn’t stay, it became loose rotating around. thanks
Do you mean the copper plate or the black plastic?
how do you get the black part that says sonnar back on? its loose and wont stay on
Hello there, I believe its sticked on with double sided tape.
Many many thanks for your post on fixing this issue with the focusing ring. Just happened to mine, maybe it was accidentally squeezed while it was in my bag.
Cheers!
I found my 35S lost one screw here, it’s still useable but can sway a little bit. I want to buy a screw but don’t know the type of this screw. Do you have any idea? Thanks a lot.