This is an Aftermarket Fisher 5804 Hex Nipple 1/4"
Straight union, this is 1/4-20 pipe thread double male ends
Western on the old cable pumps as number 25519, 25519K
Fisher used it on the under hood belt drive pumps as number 5804K
Meyer and Diamond also on the old under hood pump kits as part number 8752101 004 004.