I agree with Kurt on his point, and I have one of my own to add:

One often overlooked point in numbering specimens is to avoid the consequences
of  dermestid beetle larvae infestation. Frequently we will have shells in
which some part of the animal remains. It may not necessarily be odiferous,
but will be quite dry...just what the larvae like, and that is sufficient to
draw them to your drawers. Dermestids find paper labels just as palatable, and
I've seen the results...half-eaten data slips with the data irretrievably
lost. If you are lucky, you might be able to patch it back together using your
catalog.

I view my collection in terms of "forever", meaning i don't want to see it
turn into an assortment of interesting baubles after I am gone due to careless
handling. Far too much effort has been spent building it to take such chances.
I've seen the state of more than one  personal collection upon donation to
museums, and the resultant mess of mixed up data slips, lost data slips, eaten
data slips - usually the result of handling by relatives before deciding to
off-load the collection to a museum. I never want that to happen to my
collection. Numbers on the shells can easily be matched with the catalog for
the information. (Of course, you could donate your collection while still
living and avoid most of these pitfalls).

So I number my specimens, and make sure to use a high percentage rag archival
grade of paper for labels, and black indelible ink to write the labels.

A scientifically valuable collection is valued for the data associated with
its specimens...why take chances with losing that? Many of us use that value
as a basis to help justify the reasons we collect...I know I do...and I intend
to make certain my collection remains "intact", despite what may happen to me
along the way.

Curatorially,
Ken Zentzis
Wichita, Kansas