It would be a lot easier if the hives were not exposed to weathering.
If you have good paint jobs on your bodies t seal the wood, there are
digit stickers on rolls, everywhere from 1/4 inch to one inch available
from a number of places.  Local hardware stores can often order them for
you.
Another source is animal tags made for cows and pigs.  A local dairy man
showed a catalog to  me a few years ago.  The tags wer available i bright
plastic an metal.
 
I got a catalog a few weeks back that I will try to find and send out the
info.  They had metal tags with sticker backing and rivet/nail holes at
each end.
 
If you really wanted to get fancy (and honey was selling for $5/pound)
I could set you up with rf tags that could be embedded in your hive boxes
and read from ten feet away.  A computer with a database could geve you
complete history for that bottom board, body, or colony.  It would also
be a good way fo proving stolen property, they can be completely hidden.
(I am an electronic engineer and have been thinking of ways to automate
record keeping if I decided to go beekeeping full time.  Logic and poor
return on investment prevent me.  I have seen family lose money in farming
and beekeeping before.  Anyone need a condultant to computerize their
beekeeping business?)
 
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+    Raymond J. Lackey                                     +
+    Beekeeper 10 years with 25 colonies on Long Island, NY+
+    INTERNET: [log in to unmask]                       +
+    Mail: 1260 Walnut Avenue, Bohemia NY 11617            +
+    Home Phone: 516-567-1936  FAX: 516-262-8053           +
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++