I did some numbers quite successfully not to long ago.
In Corel Draw, I have a script that rounds the corners of a polygon,
so I took some block numbers and rounded the corners to 5/8" (for a
1/2" router bit), and printed them on a laser printer. I then ironed
the paper onto a scrap sheet of MDF (laser printers use heat activated
ink! A trick I learned from this forum), and using a skill saw and a
router, I carefully crafted that into some nice templates. I then
taped those to the back of some glued up cedar (so the numbers
appeared backwards...), and using a pin router, routed the front. I
then used a carving chisel to add texture to the background.
I thought I could get an inverse form easily by using plaster of
paris, but that didn't work (at least on my first attempt). One of
these days I'll get some free time, and I'll try another method.
Here's some pics:
If you'd like, I can send you a pdf with some numbers (you'd have to
give me the height and router bit size).