Unusual dynamics notation

[RhinoHaggis]

I'm transcribing a score with odd notation conventions, and I'm not sure how to interpret them. Here's a page showing dynamics:

The two parts are two violins.

Look at the p-slash (?) in the first measure. Has anyone seen this before?

From 300 pages of context, I currently read this as the dynamic p. But it's clearly not the same symbol. The calligraphy is consistent throughout the score. You can see above, the strokes don't match either f or p . Pianissimo is marked with two p's (last line) , so the slash doesn't seem to be an augmentation mark. mp and mf are likewise fully marked. But if it's not a duplicate of one of these.... what is it?

Now consider this guy:

... so it's f.

Or is it?

Three lines. Too narrow to decipher at a reading distance, but the strokes are meticulous! Is this fff ?? I tried this interpretation but consistent application leads to absurd (IMO) dynamic changes unrelated to the music, and out of character for the composer (L. Minkus). It's not sforzando, which you can see in the first image, with the top of the z as horizontal line of the f.

Lastly if they're markings peculiar to the violin, I've never seen anything like it. Any help is appreciated.

[The score is Russian. Two-violin reduction (répétiteur) of of an orchestral score. (Probably) Early 20th-century copy of a (probably) turn-of-the-century original.]