The master data file will have a syntax that looks like this:

e.g., mast13.dta

This example would be master version 1.3

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A matching SPSS definitional file will accompany the master data file:

e.g., mast13.sps

Such an SPSS syntax file will define the variables, names, value labels,
and create derived variables with compute/transform statements.

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A matching SPSS system file would be named in a similar manner:

e.g., mast13.sav

Thus one actually only needs the master13.sav to run analyses.
The SPSS system file will be created to be compatible with lowest
version of SPSS available to the three sites.  At present, it works with
all Windows versions of SPSS (I think).

I also have Lotus and Excel versions available with .wk1 and .xls 
extensions.

SAS and SYSTAT forms of the system file will be available eventually.

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Descriptive info on the master data file structure will also be available in
two files:

Describe.txt
and
Version.txt

The former will detail the data structure in the .dta file, and elaborate
on the basic information available in the masterxx.sps syntax file.
The latter will describe changes made in each successive version of the 
master data file.