Sights may have been altered privately
"Can anyone tell me what the front sight post and blade elevation marking of -05 is ? "
Sounds like it might be an m/38 front blade. To be sure, you will have to measure the thickness of the blade. An m/96 (original long rifle) has a blade that is 2.2mm wide at the top. The m/38 (short rifle) blade is 1.7mm wide, probably with the idea of providing the same apparent width on the shorter barrel. AND these blades were made in 12 different heights, from -2 to +0.75mm in 0.25mm steps.
The marking -05 thus indicates a blade that is 0.5mm shorter than the standard height.
So why would someone make this change?
- Because the m/96 backsight leaf starts at 300 meters! To get on target for 100 meter shooting you have to fit a taller blade. And the m/38 blade is 1.5mm taller than the m/96 blade. An m/38 blade stamped -05 is therefore 1.5-0.5 = 1mm taller than an original m/96 blade!
So it seems that the blade was swapped out by a target shooter, who is therefore the prime suspect for having soldered the backsight. I cannot imagine that an importer or dealer would do that to an complete m/96 in usable condition, as it would not increase the value of the rifle, rather the reverse. Unless, of course, the whole rifle is a "bitsa".
If my hypothesis is correct, then it would be a good idea if you could post a photo of the backsight, as that is very possibly also non-original.