Here are some notes on cleaning the rangefinder should it be necessary. The instructions are the same for the Agfa Record III and for the Ansco versions.
Taking the top cover off an Isolette or Record
Work on a soft cloth surface (white tea towel or similar) so that anything that falls does not bounce away.
First check you have an empty spool under the winder knob. You don't want the mechanism to fall in when you remove the winder knob.
Insert the end of a screwdriver into the side of the spool to help keep it rigid, and then turn the winder knob *clockwise* to unscrew it. This is a reverse-thread knob, so to unscrew it you must turn it in the opposite direction from the winding arrow. It may be stiff and hard to move, but it will unscrew by hand.
With the later versions of the camera, look into the opposite film chamber and move the spool holder out of the way. You will see a screw head at the top. It needs a long thin screwdriver to tackle this, but it is a regular thread - unscrew anti-clockwise.
The earlier versions have a depth of field disk. Remove the two small screws and the plate and then undo the larger screw underneath.
Finally, there is the small screw at one end of the top cover. Be sure to get the right size of jeweller's screwdriver to avoid marring the screw head.
The top cover should be lifted off carefully so you can see how the shutter pin is situated. This will probably fall out, but put it to one side for later.
The rangefinder cover has four screws, one of them is smaller than the others. Carefully unscrew and put aside, and then lift off the top of the case.
You can use an air duster spray to clean the semi-silvered mirror, but nothing else - the surface strips off too easily. The other lenses inside can be cleaned with a glass cleaner on a bent cotton bud if necessary. The front-surface mirror on the focus arm is also delicate and should only have the dust blown off.
Lift the end of the spring to the front of the mirror and undo the screw that holds the focus mirror arm. The pillar that holds it usually has heavy grease on it that needs cleaning off. It should be regreased with a light grease. There's some debate about which grease is suitable - I use a copper based grease which has always worked well.
You can work on the focus wheel before replacing the arm.
Ideally you should use a dropper for both some Ronsonol Lighter Fluid and another one for the Gun Oil. I cut small pipettes from old plastic ear buds as you only want small drops. If you flood the area you'll need cotton buds to dry it off as quickly as possible.
Lean the body backwards a little so you can see how the rangefinder wheel actually has a hollow 'bowl' appearance. You can drop some Ronsonol into the dish of the wheel and also put a drop onto the head of the visible thread in front. Work the wheel backwards and forwards for a while. It should become loose and smooth very quickly.
The problem is that Ronsonol dissolves the old grease, but when it evaporates the old grease can solidify again.
So ... once the Ronsonol begins to evaporate add in a few drops of Gun Oil in the same spots. The Ronsonol will lead the Gun Oil into the old grease where it will soften any old grease and blend with it. Work it backwards and forwards for a while.
Use a cotton bud to remove the excess oil from inside the wheel.
Leave the top of the camera open overnight, and then check the smoothness the next day. You may want to do this process a second or third time. Gradually any old grease on the thread will be thinned out by the addition of the oil.
Add a little fresh grease to the pillar of the focus arm. Move the long spring out of the way as you refit it and then lift it back into position. Screw it down, but check it is not too tight. Check the movement of the focus wheel and then put the lid back on the rangefinder box.
There is info online (somewhere) on dismantling the focus wheel and its nut and thread. It's complex and needs a special tool, and then considerable re-adjustment afterwards. I've never done this because I have never needed to. The Ronsonol and Gun Oil combination sorts it every time - and I have probably done dozens of them.
With luck the vertical alignment will not need adjusting. One point, if the vertical adjustment needs doing (a single screw) it must be done before the horizontal. If you do the horizontal and then the vertical, you have to do the horizontal a second time!
To adjust the horizontal focus you work on the wheel. There is an inner and an outer wheel - the designs of the grip-screw positions changed over the years.
Loosen the outer wheel - it has the distance markings. Now you can turn the inner wheel so that the lenses and mirror will line up for infinity. I use a vertical telephone mast about two miles away, so it's quite easy to get the overlay spot on.
Now you need a grip to hold the middle wheel in position while you turn the outer wheel so that the infinity mark is at the top. Tighten the grip-screws again.
Put the shutter pin back in position. Carefully lift the top cover over it, ensuring that the pin engages and the edges of the cover come down fully in position. Refit the winding knob first. Then refit the screw under the film reminder or DOF disk, and finally the screw at the end of the cover.