Learning About Viking Age Turtle and Trefoil Brooches

This project started a bit more than two years ago.  I had been developing a set of early Norse woman kit (Viking age) and had sewn dresses and a coat, woven trim, made shoes and a bag... but there was one glaring omission... the large turtle brooches that affix to the apron straps, and a trefoil brooch to hold the coat closed.  I strive to make all the things I wear to events myself, and really wanted to design and make my own brooches based on period examples, but there were some aspects of the project that I couldn't wrap my head around.  Though I had done metal casting before, this would require a more complicated two part mold than I was familiar with, and I wasn't clear about how the back of the brooches and the pin assembly was fashioned.
So I started with what I knew, and sculpted models of the brooches in clay (polymer for the trefoil and earthen clay for the turtle brooch).  I was inspired by the finds from Birka, as well as a very simple turtle brooch that now seems to be referenced only on Pinterest, unfortunately.

Last year my partner helped me cast a mold for the front of the brooches with Mold Max 60 high temperature resistant silicon.

Then the project sat.  I thought about how I could do the backs, and kept looking at pictures of extant finds and modern reproductions.  When I could see how it might work, I used additional clay to model the backs of the brooches with tabs that would be drilled to hold the pin assembly, and other tabs that would be bent to hold the tip of the pin in place.

The casting process went quite smoothly, even though my small pewter ladle required several scoops to fill the large brooch.  As a result, some of the metal's impurities were incorporated into the pieces.  But for a first try, the pours went very smoothly.

Drilling the holes in the tabs to hold the pin felt like the hardest part of the entire process.  But with some patience, I was able to complete the pin assembly.  I'm so looking forward to wearing them this weekend to the SCA event: A Market Day at Birka!
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At some point I would love to make a set of these in bronze, possibly using precious metal clay. But for now I am more than satisfied.