[Ietf-languages] Khmer orthographic reform

[Élie Roux <[e-mail]>]

Dear all,

I have some data in Khmer that I need to use two tags for:
- one for Khmer as written before the orthographic reforms of the XXth c.
- one for Khmer written according to said reforms

The situation has been explained to me as follows:

"""
The reform is not exactly clear cut, unfortunately. Let me see if I
can find any sources. We don't know much about pre-20th-century
reforms; this is an area that needs more research. But a reform
process had begun by the early 20th century, and it culminated in the
compilation of the first comprehensive Khmer-Khmer dictionary, under
the editorship of Juon Ṇāt (Chuon Nath) and others. The first edition
was published by the Institut Bouddhique in 1938. Although there were
some additional spelling reforms in the 1960s and 1980s, still most
users of the language today still refer to the fifth edition of the
Institut Bouddhique dictionary, printed in 1966.

Manuscripts produced after the 1920s or so may show reformed
orthographies, but old spelling systems remained in place in some
manuscript traditions for several more decades, particularly when
copying directly from older texts.

Books printed after the 1920s almost never have pre-reform orthography
(19th century books and dictionaries do, however). Many Cambodians
today have never encountered a pre-reform orthography text, though it
is not hard for them to learn to read it.
"""

What is IANA policy with regards to this kind of situation? Is it
reasonable for me to propose a "-pre1966" or "-pre20c" subtag for the
strings that use the old orthography?

Best,
-- 
Elie