This item appears to be the same as any beaker, bottle, container, decanter, flask, jug, etc.
It has magical properties, but detection will not reveal the nature of the flask of curses.
It often <d% = 26%+> contains liquid substance too, or may emit smoke.
<d%
01-50 = liquid
    01-50 = normal liquid <make subtable>
    51-00 = potion
51-00 = as [eversmoking bottle]
>
When the flask is first unstoppered, a curse of some sort will be visited upon the person or persons nearby (it will subsequently be harmless).
The suggestions give for the curse reverse of the cleric [bless] spell,
and those stated for typical curses found on a scroll are recommended for USE here as well,
or some monster can appear and attack all creatures in sight, etc.
<link=curse scroll>
<link=make d10(I-X) table, 10 links>