Duplicate FBs
From TrigpointingUK
The numbers on the flush brackets on the side of trigpoints are nearly unique but, perhaps surprisingly, there are some duplicates.
S2363 is on both Corley Resr TP2413 and Overton TP5261
S3351 is on both Dagnam Park TP2716 and Layhams Farm TP4378
S3355 is on both Bellevue TP1248 and Chelsham Court TP2138
S3358 is on both Box Hill TP1553 and Knockholt Beeches TP4287
When Non Pillar Flush Brackets are included, the list becomes even longer
S6502 is on both Long Crag TP4517 and at Gurnos BM22870
The Bench Mark Database has a long list of such anomalies.