Barefoot lists seven 1920 surcharged documentary revenues. In my experience, they are all scarce.
In black:
1.00F/50c
2.00F on 1.00F
2.50F on 1.25F
In red:
1.00F/50c
2.00F on 1.00F
2.50F on 1.25F
3.50F on 1.70F
1.00F/50c
2.00F on 1.00F
2.50F on 1.25F
In red:
1.00F/50c
2.00F on 1.00F
2.50F on 1.25F
3.50F on 1.70F
I was especially fortunate to find the 2.50F/1.25F (shown above) used on a death certificate issued on 8 February 1923 at Troisvierges for one Peter Heinen (below).
The document is also interesting because the German text has been translated into French on the reverse side.
2.50F surcharge on 1.25F
Documentary
Death Certificate for Peter Heinen
Troisvierges Commune
8 Feb 1923