Obviously, this design could be varied endlessly by using different charms, findings, beads, thread colors, etc. It's quite simple. There are no split rings - but does require the use of 2 shuttles, and they are "switched". In other words, shuttle 1 trades places with shuttle 2 where indicated in the pattern, which is available as a pdf in my Etsy shop. BTW, there are many Etsy sellers who offer interesting charms and findings for sale. Of course, if you really want the same tiny keys I used, they are available at Bello Modo.
Even though this is so simple a pattern, it did take some experimentation time for me to figure out the stitch counts so that the tatting would take shape naturally without being forced. I think this finished design has major improvements over an earlier attempt.