A gaff deck I recently picked up (Copag 310 Gaff Deck) appears to have cards for a number of popular packet tricks, e.g. Ultimate Three Card Monte, MacDonald's Aces, Twisted Sisters, B'Wave. I'm very familiar with those effects, and immediately recognized the cards required for them.

But I'm drawing a bit of a blank with other cards in the deck. They could just be generic gaffs, of course, since double facers can be used for routines like Anniversary Waltz. But I suspect that at least some of these have been deliberately chosen with specific packet tricks in mind.

Taking a look at this list of remaining gaffs, do you recognize any routines that some of these are commonly used for?

8x Blank backed: 8/9/10/J/Q/K Spades plus 6S and 6H
4x Double facers: Four Queens (QH/QD/QS/QC) with indifferent backs
7x Double facers: 10/J/Q/K Diamonds + J/Q/K Clubs (all identical on both sides)
1x Double facer: split face KH/KD and split face KS/KC

It's possible this last double facer is to be used in conjunction with two split faced Kings that are included (KH/KD + KS/KC), although I think it's more likely those are intended for Tw*st*d S*st*rs along with half a dozen red/blue backed blank facers.

The remaining cards are obviously more generic:
4x Blank with blank backs
6x Blank with red/blue backs (presumably for Tw*st*d S*st*rs with the split Kings)
14x Double backers (different combos of red/blue)
2x Reveals (Joker with JH reveal, KH with QH reveal)

Any ideas about other tricks that might use some of these cards? Does anything look familiar here? I'm especially curious about the blank backed Spades cards, and the seven double-facers which are identical on both sides.

(NB: A video here shows all the cards in the Copag 310 Gaff Deck one at a time.)

I think I've figured out some more - the two blank backed sixes can be used (together with some blank faced cards) for the F*ct*ry M*spr*nt (Wagner) and P*r*m**nt (Colombini) routines that are included as bonus effects in Michael Ammar Easy to Master Card Miracles Vol 4 and 5. I should have realized that myself!

At this point I'm mainly still baffled by what packet tricks or routines these might be intended for (besides obvious utility cards with application to a gazillion tricks):

6x Blank backed: 8/9/10/J/Q/K Spades

7x Double facers: 10/J/Q/K Diamonds + J/Q/K Clubs (all identical on both sides, i.e. the 10 of Diamonds is printed on both sides of the same card)

These could perhaps also use other blank faced or backed cards.

Any ideas?