Summary

1:3 scale model of the Atari 1050 floppy drive ( http://www.atarimuseum.com/computers/8BITS/XL/xlperipherals/atari1050.html )

This should fit an SD card reader similar to this one, once removed from its plastic case:
http://www.amazon.com/eForCity-Memory-Reader-Adapter-Smoke/dp/B000Z9R2QQ/

Made to match the 1:3 scale 800xl:
http://www.thingiverse.com/thing:625596