I want to second the motion to mark all artifacts in a way less-detachable
than tags.  I am a registrar/exhibit preparator at the Atwater Kent Museum
(Philadelphia's city history museum), and am presently engaged in a
comprehensive inventory of what we currently believe to be over 100,000
artifacts.  A stunning number of them are unlabeled, and all too often we
find a paper tag at the back of a shelf, bearing a number that has no
relation to any object on any neighboring shelves.  Or, worse yet, we
sometimes find a tag from the museum's early days that simply says "Gift from
Mr. (VIP Historical guy)" lying at the back of a cabinet nowhere near any
artifact.  Our conclusion is that TAGS ARE UNRELIABLE.

Our current (not yet official institutional policy) operating procedure is to
paper-tag 3-dimensional artifacts in addition to "painted-on" numbers applied
with a technique appropriate to the material of the artifact.  The logic of
this is that the removal-resistant number should be in an inconspicuous place
to facilitate exhibition, etc. and the easily-removable tag should be
prominent to facilitate identifying the artifact in storage without having to
handle it.
I hope this helps, and may no one else ever again make the mistakes of our
dearly departed curators of previous eras.
Adam Zuckerman
All opinions expressed are purely my own and not necessarily those of any
institutions to which I am affiliated.