Respighi concerto in modo misolidio glissando

[jgranata13]

I'm having a little bit of difficulty interpreting the glissando in the attached picture.  It can be found at the bottom of p.25 of the score (there's only one edition floating around on the internet/IMSLP).

The notes as written are:

B-flat/C-flat, A-flat/B-dbl-flat, G-flat/A-dbl-flat, E-flat/F-flat, D (natural), D-flat/E-dbl-flat, C/D-dbl-flat, C-flat.

Considering that it's intended to be played as a glissando - and specifically with the fingers 2-1 - I think there's a misprint.  To me it would make more sense as:

B-flat/C-flat, A-flat/B-dbl-flat, G-flat/A-dbl-flat, G-dbl-flat, E-flat/F-flat, D (natural), D-flat/E-dbl-flat, C/D-flat, D-dbl-flat, C-flat.

In this way, the single notes and top note of each dyad form a white key glissando, played by the thumb, and the second finger hits the black key immediately below (when there is one).

Question 1 - Is there any way that the text as written could be correct / played as a glissando with the given fingers?

Question 2 - Do you think the intention is to keep this pattern all the way through the "second part" of the glissando, or does it turn into just a white key glissando after that first octave?
My thinking is that its the latter because if it were the former, C-flat at the beginning of the line going down would have been a B-flat/C-flat dyad

Question 3 - Does anyone know what that symbol at the very bottom right below the staff means?

[anacrusis]

Question 2: seems reasonable to me that it turns into a normal white key glissando. It's not unambiguous, but since it has a single note at both the start and end of the glissando and one line instead of two, it seems reasonable.

Question 3: It looks handwritten to me. Maybe it's a pencil mark or a random artifact/dirt from scanning?

[dw4rn]

I find it likely that what you are suggesting is what was intended. In other words, my answers to your specific questions would be
1. No
2. I agree that it should turn into a white key glissando
3. No idea.. however I think you're right that it's some kind of symbol rather than random dirt.