This could possibly be it. It's a now deleted commercial service letter (I think 3049).
https://www.scribd.com/document/3641...r-C20-and-C20R
This link has a link that lets you download the entire letter in a PDF.
https://www.helikopterfliegen.de/for...?showtopic=834
Last edited by helonorth; 1st July 2021 at 00:26.