Is an automatic transmission dust cover needed?

Are you sure that you've got the right dust cover for a 904? I've got a few laying around here and they don't have that small opening on the bottom. The one for my 727 does. They don't interchange. The top 2 pics are of a 904 cover. It's hard to see but the bottom pic does have that small cover on the bottom of the shield and it is on my 727.

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