Home Forums Lever Action Central Marlin 336 Lever Actions Waffle Top Swivels ???

I have a (1951) 336SC and a (1949) 336A and both have a milled channel in the barrel and magazine tube for bolting on a front swivel.
Why would Marlin do that if the general consenus is they didn't come with swivels. The swivels on both of my guns are identical. The pic
that is circled is of the milled channel (hard to see). Am I missing something.