They were typed, the paper thin and yellowed, slipped into the return slot at night. Each began with Dear Ava, and each contained a single sentence that might have been a memory: You did the right thing. You should have listened longer. You must not let them find the spool. The signature varied—H., M., sometimes nothing at all.

It covers document formats from nearly every continent, ensuring that OCR (Optical Character Recognition) models trained on it are not biased toward a specific country's design or alphabet. MIDV-578

Here is a brief overview: