Hans Marg said below on page 1 .
They are 2/0 Jewelers Blades. I got them from Gemcuts www.gemcuts.com.au I just got the budget ones and they cut very nicely.
Marg
I prefer 1/4 INCH then I use my favourite tool the leigh D4R Pro Dovetail jig and cut splines in contrasting woods for the corners that way the corners can't part. Roly
Paul great work I have done this with a 6 deg angle on the letters so it wedges and won't come out. sticking the words on you could use different contrasting woods nice idea. Roly