So, a favor:

Would someone with the tools and skills be willing to measure up and either accurately describe or annotate a photo of this mythical tabbed washer? I'm a handy guy with a set of files and a frickin' virtuoso (in my own mind) at the grinding wheel. It's just that I've got a new-to-me bike that's just begging for a Duopar rear mech, and I'd like to be able to use my Eco.

Or could someone with the spare parts handy compare and contrast one with the tabbed front-wheel washers that have been mentioned-- or maybe a Sturmey washer? Ya folla?

I have a feeling other people than me would be really grateful.