Collapsible 50mm f/2 Summicron Question

I recently acquired a LTM Collapsible 50mm f/2 Summicron that I use on both a IIIf and an M2 w/adapter ring.

I was shooting straight into the sun yesterday and got a surprising (to me anyway) flare behavior. The pattern here looks like light bouncing off the edges of the aperture blades. Is this normal for lenses of this vintage or is there a problem here (quick and very dirty film scan of Fomapan 200 negative semistand developed in Pyrocat-HD):

I can see where that will happen- is there any oil on the outside of the blades? Tiniest bit that makes the edges of the blade shiny? Any where to the outer edges of the blades that might make then shinier than the rest of it? I see that on mine, can imagine in very bright sunlight hitting the aperture at an angle, this could happen.

These lenses are lovely, but the lens coatings are fragile. Most are close to 70 years old

Be careful you don't burn a hole in your shutter!

mshchem said:

These lenses are lovely, but the lens coatings are fragile. Most are close to 70 years old

Click to expand...

The coating on this one is pretty much flawless.