Something I've been meaning to do ever since I've had my 350 was to get the correct license plate holders for the front. I've wondered whether many w116's out there have suffered the same fate as my 350 where the original plate holders have been lost or broken but rather than replaced, have had holes needlessly drilled into the bumper to screw the license plate onto. Seeing that 4 of the 5 w116's that have passed into my posession, have had their front bumpers mutilated in this way I reckon it might be a common thing but it need not be.
The original holders, part number A1168100614, cost me about $11AUD each. The only problem is that they didn't come with screws and as soon as I get a screw that fits I'll post the size.
Here's what happens when a mechanic comes up with a solution rather than buying two $11 parts

Another example of needless drilling

Here's what the original correct holders look like

And here's how the original holders fit. The smaller part of the holder goes into the "keyhole" of the bumper and slides along. The license plate sits against the larger section of the holder and a screw goes through the plate into the brass coloured threaded section. License plate and holder become clamped onto the bumper.
Don't know whether I'm a minority here but if you're missing the holders and are on the verge of making your own mount, do yourself a favour and buy the real thing and save your bumper.