Could it have been a parts sticker that was on the belt that got melted and dragged across the surface over a couple thousand miles?

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Hard to say at this point. More likely oil from valve cover breather leak and/or fluid from underside of PS reservoir which belt runs very close to. Or perhaps greasy oil/dirt off front of engine found it's way onto the tensioner pulley and then got heated and solidified.

Will watch for these things when I put new belt on.

New belt does have a manufacturer's sticker. Not sure if it can easily be removed - kind of well adhered. Looks like they don't expect that side to be in contact.

Attached Thumbnails

 

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Graham, as you are aware the outside of the belt contacts the belt tensioner pulley and the fan pulley. The identification information, shown in the picture, is stenciled on the belt. There is no reason to remove that information as it will not affect the performance of the belt. Your engine may need a thorough cleaning if grease and grime are getting on the accessory belt.

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Fred Hoelzle

The original belts were imprinted, but the aftermarket Bando that I now have has a separate shiny sticker. It won't peel off when new. Hopefully not in service! roughening it a bit might be useful, but I doubt it it is a real problem.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5