That metal rattle is most likely the window guides, they fall off into the door. Just another thing to fix and will result in some job creep, meaning you will find more stuff to fix when you open up the door. This always happens with these cars. One little dash bulb out and the next thing you know your soldering the brackets back on the heater core. The car does sound like a very good price though when you see absolutely perfect W113's, and I meam perfect cars bring $75,000.00+. But your car could be $90,000.00 in repairs away from that. Well maybe a strech here, but you get the idea. Just look close for previous wreck damage with those headlight marks gone something was done, and done by someone not intimate with the nuances of these cars. Check the inside front fenders to see if the spot welds are in place where the original fenders were put on. I spotted a great looking black w/ red interior 66' 230SL at a local body shop. I couldn't believe what I saw. The body shop owner was very proud of his job completely restoring the car from a front collision. The gap from the hood to the front nose was about an inch wide and 1/2" low. They obviously just put the nose on and never lined it up. The whole job was wasted. The car was better off before it was fixed from a financial standpoint as it now needed to be redone, or just sell it on Ebay with some strategic photography.
And, yes it is rumor from my friend, a body man by trade that the water based paint will be required in the near future. It is already law in some parts of California. Water base paint cannot be used without the base/clear process and I don't like the look on many vintage cars, especially if you are an originality nut like myself. My friend claims the water base paint does not hold up anything like good old enamel paint. I am not sure how color and finish matching will happen when only repairing a section of a car such as a wrecked panel.
Sorry to kind of hijack your thread here with this paint talk, maybe someone will start a thread on it.
On your oil pressure, many W113's show that exact pressure and some are always pegged. I don't think it is an indication of condition, but more a condition of idle speed and oil viscosity. You really need to do a simple compression check on the engine to determine a baseline of engine wear.
But remember, you are buying an old car and anything can happen. Just this Summer I pulled out, took off at normal speed and BANG, sudden differential failure. Two months later, several hundreds of dollars and many many hours of work I have 4 wheel disc brakes and a whole new axle in my 230SL. Luckily I have a 250SL parts car, and a member here sold me a great drum brake axle, now I have a spare "original" axle and can return the car to stock at any time. Not that that would ever happen, but I can say I have an original axle and in 30 years it may be worth putting it in. And wow what a difference those 4 wheel discs make.
The very first upgrade I would do is to put in a set of $100.00 H4 Hella or Bosch headlights with 100/55 watt bulbs. for the safety factor.
