MW Collegiate has both implementer and implementor with no distinction.
OED has implementer with implementor as variant.
Oxford Reference says:
Although the variant spelling implementor predominated for much of the late 20th
century, today implementer is considered standard. Current ratio: 4:1.
It appears there is little difference between American and British English where
implementer is equally common.
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Take care. Thanks, Brian Inglis Calgary, Alberta, Canada
La perfection est atteinte Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter not when there is no more to add
mais lorsqu'il n'y a plus rien à retrancher but when there is no more to cut
-- Antoine de Saint-Exupéry
