Laos Post-Royalist Government "Varieties"

I found this very interesting cover on ebay and thought I'd share it for anyone interested in Laos (LaoPhil?? ).

The royalist government of Laos was overthrown in late 1975 and the country was renamed the Lao People's Democratic Republic. They must have had a shortage of stamps, as all but one of the stamps on this cover (postmarked August 13th, 1976) predate the name change but have the words "ROYAUME DU" in both French and Lao script manually crossed out with pen.

As each stamp has the manuscript change in a different color and style of pen, I'm guessing this was done to the stamps before they were put on the envelope. For some reason they missed one of the stamps, the 70K not being altered.

I haven't seen this modification before, but I'm not a Laos specialist and am only particularly interested in the 50K stamp due to the artist (Pierre Gandon). I wonder how catalogues would treat this sort of 'variety'?

Comments by anyone familiar with stamps of this sort are welcome. Are they common? Have they been noted in any catalogues?

Here's the cover and close-ups of the modified stamps.

Thanks for posting this cover and stamps - very interesting