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Did you do a search here for > Landis+Gyr E355 manual < ?
Here is the search results, you might find some tidbits of info looking through the results . . .
https://neighbourhood.agl.com.au/t5/forums/searchpage/tab/message?advanced=false&allow_punctuation=f...
These sorts of threads come up often for various meters, and it's usually the same sort of thing, hard to find, sometimes impossible it seems.
In saying that, I just did a quick Google on there too, and this happened to come up . . .
** Note, it is for the e350, not sure how different the e355 might be **
*** Also, I didn't try downloading this, and would not recommend it is gieneral, not sure what you can trust downloading such things ***
https://www.manualslib.com/manual/1577125/LandisPlusgyr-E350-Series.html
The search also brought up . . .
https://www.youtube.com/watch?v=2hsKoWNF1Lw
Very little else, and judging from past threads and lack of online info, you might not have much luck, but good luck in your search anyway.