depending on scenario, you could use a hopper thing that sends a pulse if an item of the same type comes in then unlocks long enough for 1 item to drop back out, then it doesn't matter data values and all that other jazz, you can duplicate it by using middle click. this type of systems is usually associated with sorting items into chests using hoppers.
Hope this helps,
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There will always be someone better than you, so you can never be the best. That doesn't mean you can't work to be the best that you can be.