Below is the form to submit your own research on Leather Shipment drop rates. All data will be reviewed for alignment to known drop rate patterns before being included in the model.
"Drop rate patterns" in this case means the known parameters of which things can drop and how much of them. For example, ore does not drop from Leather Shipments, so it's impossible for you to receive Mithril Ore from one. Also, through my own research, it's clear that Leather Shipments have the following drop pattern:
From each shipment, you receive 10 "units" (my own designation for it for lack of a better word). Each unit can be a 10-stack of any tier leather material. This means I always expect the total number of leather materials gained to be equal to 10x the number of shipments opened. As a warning, any data that does not align with those expectations will not be included in the model.
Also below is the research sheet showing the examples of that from the shipments I tested, for your reference. When you're ready, fill out the data submission form below.
Please also consider posting your data to the GW2 Wiki's page on Leather Shipment Drop Rates.
Thank you once again for your contribution!