I have a very similar Swedish razor - can't remember if it is an E A Berg or a Hellberg, with the same dropped spine. Although it seems overkill for a frameback with the thick spine and hollow grinding, I suppose it could be for that reason. But it could just as likely be for sitting a hair-cutting guide on - I have seen a few old smiling razors with that design. The one below (Berg, Solingen) has a guide fixed in place - no cutout or drop in the spine though, but the same principle:



The guide is simply fitted by tightening the screws in the above example - there is no hole drilled in the razors spine to take the central screw like I have seen in some examples. If the guide was shaped to fit on top of the spine and 'spring' tempered so that the side flaps gripped the hollow, then the screws would be unnecessary - I have seen this type of guard, too.

Regards,
Neil