Interestingly I flew green maps last night to Berkley using bowl of riches. The drop rate was dire. I didn't count the number of flights completed, but it was essentially as many as I could manage in the 1 hour of the bonus. Completed 3 collections (EDIT: I would guess I completed 80-100 flights). I have had better drop rates on those maps without a bonus active.Yesterday, I tried a map to Perth (green space collection - with turboprop)
First with bowl of riches (BOR) - this had no effect: 0 Drops out of 20 flights.
Second: Golden Dice (GD) + BOR: 6 Drops out of 20 flights, than 8/20.
Third: Only GD: 8/20, than 10/20.
Thus: BOR totally useless for map flights. Petit told me, BOR is only usefull for event collections (so called "quest items") which explains the bad performance doing space collection maps.
The icon under the description in the game (airplane with a box) is thus misleading as it is the same in GD, BOR and Spy Glass whilst the text is clear (if you know what quest items are...).
The symbol is indeed misleading, as it suggests that it gives a drop rate of +150% for collectable items dropped from flights. In fact I'm sure it is the same symbol as shown for the golden dice bonus.
Post edited - see edit note in text.