This was the old Disney TV series Zorro. Originally filmed in B&W, Disney later colorized it (and did a quality job of it, too). Both versions are now on DVD ... if you can find them. :) This particular test was of the first episode.

The "fixes" were rudimentary, just for the proof-of-concept. In a paint program, the YouTube snapshot (shown here actual size) was heavily smeared to reduce the pronounced compression artifacts. For actual video processing with an Avisynth script, a proper deblocking filter would be a better start.

The Blade Runner laserdiscs are not this bad. (That's why I suspect there must be some odd variations in the Blu-ray that would require fixing, too.)