From the Readme file:

> The SIMM Stack contains memory configuration information for
> Macintosh computers and LaserWriter products.

This is version 4.7

A note about the downloads available above:

 * The first file available from above is a Disk Copy image, ready
   for emulators
 * The 2nd file available from above is a sit.hqx file

What are SIMMs?

> A SIMM, or single in-line memory module, is a type of memory module
> containing random access memory used in computers from the early
> 1980s to the late 1990s. It differs from a dual in-line memory
> module (DIMM), the most predominant form of memory module today, in
> that the contacts on a SIMM are redundant on both sides of the
> module. SIMMs were standardised under the JEDEC JESD-21C standard.

Read more about SIMMs at <http://en.wikipedia.org/wiki/SIMM>

Compatibility
Architecture: 68k PPC

The SIMM Stack requires [HyperCard version 2.2][1] or greater in order
to function properly.

  [1]: http://macintoshgarden.org/apps/hypercard-241