Shays's Rebellion (follow-up #2)

[Barnhart]

Further looking about found

NewspaperArchive.com ...

Shays' ....... 173
Shays's .....   23

ProQuest

Shays' .....  198
Shays's ...  282

American Heritage Word Frequency Book

Shays'  ..... 2 (at the 8th grade level)
Shays's ... 0

In the DA there are 4 quotes: two for Shay's; one for Shais; one for
Shays'.
The form in the Thorndike-Barnhart High School Dictionary (c. 1973) is
Shays'.

Is it true that words ending in -s when made possessive used to be more
commonly -s's?  I seem to remember my 5th grade teacher saying something
along those lines back in the 1950's.

Regards,
David

barnhart at highlands.com