289 oil pickup screen with dimples?

[CharlesTurner]

I'm used to seeing at least 65-66 289 engines with a smooth top oil pickup screen.  Does anyone know what the dimpled one is from or if it is simply an aftermarket piece?  Any advantage/disadvantage to using one with the dimples?

Thanks

[J_Speegle]

Seem my share of this version. Since I don't believe there are any markings on them I don't know their source or if they were all original.

Dimples would likely reduce the flow very slightly as I think they were designed to keep the screen from flexing

Sorry no smoking gun from me on this one 

[TedS]

Looks like the Melling and Mahle offerings have the dimples. My first thought was to prevent vortexing but I agree, probably to prevent a full collapse of the screen.

[gt350hr]

  IIRC they came along in '69 or 70.