When I bought my new camera (see my last blog post) It came with a slightly sorry-looking TP roller blind shutter. Granted, there was no name stamped onto this thing, but the basic principles seem to be the same.
Personally, never having owned one of these shutters, did not know how to operate one, so it was hard to establish which parts were there, and which were missing. After a good bit of digging the internet I found a few well-illustrated articles on how to replace the blinds and this helped me a great deal in figuring out how this thing works.
So how does it work?
When the thing functions properly, you just have to set the required shutter speed, you pull the spring to wind the mechanism and you press the shutter. Presto!

The lens removed. I had this little block in there, not sure it’s really needed although it will help guide the string and blind

This side shows the shutter speed it’s set to. The gap in the middle might just be for a screw that’s gone missing.
To Operate:

To decrease the shutter speed, push the little level downwards. The spring inside the bottom roll will release it’s tension and the dial on the other side will drop to a slower speed.

If your speed setting is not decreasing, help it along by pushing this little toggle gently upwards.

To cock the shutter, pull the string. Mine clicks once into place for an opened setting (handy for long exposure times) but keep pulling to the second click and you’re good to go. Keep in mind to set the shutter or keeping a lens cap in place before opening your darkslide!

To fire the shutter, push this little tab outwards. I’m sure there used to be a firing mechanism attached at some point in time, but that’s gone. The brass bits directly underneath might be part of a timed or remote shutter release.
And that’s it! Not that hard, until you find a few bits missing. I found mine like this:
It needed some wood repairs (which were my own fault as I could not get this darned thing off the front of the camera), the string and some screws replacing. I’m missing the original loop that holds the string into place, the (remote) shutter mechanism and something that once lived just over the shutter speed setting dial, which may have just been a screw. Lucky for me, the spring mechanism for the shutter speeds and most of the curtain were still intact, and, as it turns out, I had all the needed parts to make it work again.
First, I repaired the wood as that was the easiest part.
Second, the roller blind. I used pieces of adhesive bandage tape, then, when they tore again after only 1 day, I re-enforced them with fabric glue. I forgot to do this at this stage, but this is also a good time to check for fabric integrity and any light leaks. Make repairs where needed and give your blind a fresh coat of acrylic black paint.

Repair the break(s). I used bandage tape, re-enforced with fabric glue. Clamp them down and leave to cure for 24 hours.
Then, the chord. I had a spindle of green chord of a similar thickness of the remains of the pull string in the shutter. I pulled it through, knotted it to keep it in place and wound a good part of it onto the string (anticlockwise, so over the top towards yourself). You’ll need about 30 cm as you’ll need to accommodate the full length of the shutter and then some. Guide the string into the little groove on the side of your shutter and pull it through the little hole at the bottom. Traditionally, the end would hold a ring or wooden toggle to secure the thread, I’ve used a safety pin till I can find something better.
Finally, I was ready to build this thing back up. Make sure all your repairs are done and dried. Insert your top roller back into it’s place (you will have done this already if you repaired your string) and make sure you got the left side in its little hole. Slide the brass plate over the other, radared side and screw it down. Keep the top roller into place with that small brass plaque that looks a little like a duck face.
On top, screw the shutter cog into place. Make sure you align this properly, so that your first click actually fully opens the shutter and your second click fully shuts it. It will look like this:
Then, place the shutter back onto the whole thing. The lower end sits just underneath the brass plate (look for the slots) and the top screws into place.
And that’s it! Congratulations on your repairs and have fun using your new (old) shutter. If you want to read an excellent tutorial on how to make and replace your roller blinds, I’ll gladly refer you to paulewins.com and Lungov.com.