i have seen in my life two guid collisions already. and i'm not that old. One of them was genuine - generated by different systems, and it was caught when load

i have seen in my life two guid collisions already. and i'm not that old. One of them was genuine - generated by different systems, and it was caught when loading data from one to another - object had same ID, but different underlying type. Other one was due to 'error' - two systems(by different companies, supporting the same data exchange standard) used magic hardcoded guid that turned out to be the same. Both of those systems have full audit trail - each change created new row in database and IDs were formatted as {NAMESPACE}.{GUID}.{TIMESTAMP}. Mutation of an object created new entry with different {TIMESTAMP} part. Namescapes are mandated by standard, so different systems can have the same namespace value.