This is the current NASA tide gauge data, which shows 17 cm of sea level rise from 1870 to 1980, or 1.8 mm/year

Here is the 1982 version, which shows about half that much rise.

The next image overlays the two at the same scale, normalized to 1880, showing how the data has been altered since 1982.

And here is an animation with markers.

This is bad, but it is much worse than it seems. The data tampering has accelerated as time went on. NASA has quadrupled 1955-1980 sea level rise since their 1982 version.