Cooper tried to allay Rorer Group’s takeover fears.

Cooper Laboratories mailed Rorer shareholders a letter soliciting their proxies in support of a resolution requesting Rorer’s directors to eliminate an anti-takeover measure. The rule, to be considered at Rorer’s annual meeting April 23, would force an acquiring company to issue its stock at half price. Cooper said it is not seeking control of Rorer and does not plan to do so.