W J Jeffery records are privately held by a Mr. Thomas Friedkin out of Houston, Texas & it is extremely difficult to get info.
You might try "Pugwash" here to see if he can help you out.
The process, if successful, can take 6-8 months and will (maybe) include a photocopy of the surviving daybook page.

See comments in my .577 Jeffery thread:
http://forums.nitroexpress.com/showflat.php?Cat=0&Number=271827&an=0&page=2#Post271827

Good luck,
Mike