Currently Numista lists P# 31 varieties as ND with printing ranges. https://en.numista.com/catalogue/note206823.html
The notes P# 31a and P# 31b do have dates on them as seen on Bank Note Museum page http://www.banknote.ws/COLLECTION/countries/ASI/LAO/LAO0031.htm
Shouldn't dates be recorded as actual issue dates?
I also sent message to referee (I missed seeing name until after making this post).
Will