This is Micrasterias americana, a small desmid that used to be very rare here in the Netherlands. But it is becoming more and more widespread.
Funny, but it reminds me a bit of Coca Cola and McDonalds.

I stacked it from 5 or 6 images. 25X neofluar obj. darkfield. I agree with Wolfgang that manual stacking often works better with microsubjects but this one worked o.k.
Wim
