While exploring the Belgian enclave cities within the Netherlands, Baarle-Nassau (NL) and Baarle-Hertog (BE). I uncovered discrepancies between my field measurements and the archives concerning measuring numbers intended for estimating the national boundary length.
Within this installation, a pair of tapes is designated for accurate measurements. One tape displayed '7.50m' despite being a 20m tape, while another indicated '20m' on a 7.50m tape. Surprisingly, both tapes measured the same actual length, approximately 5.5-6m.