WSPR version confusion

Investigation whilst developing Evolution of WSPR revealed some potential issues relating to certain WSPR versions.

The WSPR 2.0 manual states:

Please note that messages with compound callsigns or 6-digit locators will not be properly decoded by WSPR versions earlier than 2.0. Further details on message formats can be found in Appendix B, and in the WSPR source code.

So, lets mine some data.

A report derived from the wsprnet.org archive of December 2015 follows.

postgres=# select ver,count(*) from (select distinct reporter,ver from spots) as a group by ver order by count(*) desc;
    ver     | count
------------+-------
 2.0_r1714  |   377
 2.12_r3617 |   322
 1.6.0      |   208
 0.8_r3058  |   174
 1.6.0-rc1  |   167
 1.7.0-deve |   103
 1.6.1-deve |    81
 2.21_r2286 |    54
 2.11_r2263 |    52
 1.6.0-rc2  |    51
            |    45
 1.6.0-deve |    24
 4.0 r4889  |    19
 4.0 r6053  |    14
 4.0 r4171  |    14
 4.0 r5489  |     9
 0.9_r4178  |     7
 3.9_r2840  |     6
 2.20_r2279 |     6
 4.0 r3015  |     4
 2.20_r2283 |     4
 2.11_r2250 |     4
 3.00_r2326 |     3
 0.9_r5279  |     3
 3.00_r2328 |     2
 4.0 r4456  |     2
 0.8_r3575  |     2
 3.00_r2513 |     2
 2.21_r2288 |     2
 0.6        |     1
 1.12_r1177 |     1
 4.0 r4522  |     1
 3.0.1_r255 |     1
 4.00_r4171 |     1
 2.10_r2165 |     1
 3.0.1_r246 |     1
(36 rows)

The version I am currently using is 1.6.0 which is from WSJT-X, the latest version downloaded days ago from the ‘official’ site.

Does that qualify as WSPR versions earlier than 2.0?

You can see by the list that 2.0_r1714 is the most popular version, it is quite old now, the manual is internally dated more than six years ago (Nov 2009).

Confusion reigns.