Online tool for OMR compliance

[N. W. Perry]

Nope, prolly a typo. Both should be 1.

This is the same discrepancy I inquired about here. I likewise assumed it must be a typo—but should they not both be 2? The spec says:

The first set using a given number would be understood to never contain the qualifier however numbering should start with the oldest set and some investigation should be done in existing set databases.

This suggests, if I interpret it correctly, that the "-1" qualifier is implied but never included in the filename, which I would guess is to avoid renaming in case a second set is released using what was previously a unique set number.

However, you've also pointed out that OMR compliance is a guideline rather than a firm regulation, so for a compliance-check tool it probably makes sense to allow a "-1" qualifier if present, but not to return an error if it's absent. (And since many existing models use the "-1", it probably also makes sense to align the spec to the status quo rather than the other way around.)