Jeff,

A more systematic presentation of the early El Primeros is available in the following three posts, which are stickies at the top of the same forum you found

http://forums.watchuseek.com/f27/preliminary-notes-collecting-early-el-primeros-general-remarks-431440.html

http://forums.watchuseek.com/f27/preliminary-notes-collecting-early-el-primeros-specific-models-431451.html

http://forums.watchuseek.com/f27/overview-vintage-zenith-el-primero%92s-all-stainless-steel-models-1969-1975-a-586997.html

: Here is an interesting thread from WatchUSeek covering some of
: the early El Primeros; as you might expect, LouS is a good
: contributor to the discussion!!

:
: http://forums.watchuseek.com/f27/vintage-zenith-el-primero-questions-415101.html

: Wish there were a good website indexing all these early El
: Primeros. Gets complicated when we have only the model numbers
: (787, 3817, etc.), rather than the model names (Autavia,
: Carrera, Daytona, etc.). We know how hard it can be when we have
: the model names; far more difficult without them.

: Jeff