In 1937 they changed the S code bayonets to the firms name. However, I am seeing 1937 dated S84/98 bayonets that are still using the S codes. How rare are 1937 dated S codes S84/98 bayonets?

Hi. 1937 S/ coded are not specially rare, except for some manufacturers such as S/241.
I would say it's as common to find a S/ code 1937 than a manufacturer name. S/155, S/174, S/178 and S/245 are pretty common.