Apologies I intended to get this completed today but farm issues intervened. I've had time this evening to dig out the saved prop blades and screws and have a quick look so here are some preliminary findings.
Note that the screws I've looked at are a mix of Dji & third party; I did not store them separately, and have not separated them out yet. I have 19 used screws, and 14 used prop blades.
I need to check them with calipers tomorrow to attempt to separate the Dji- and TP (third party) machine screws. There are differences but they are very subtle. I have new, unopened sets of both screws I can measure to get a baseline that I hope will allow me to identify the used ones as OEM or TP
o All the saved screws' heads are flat on top, flat underneath, with no countersink
o All appear to have the same length unthreaded portion
o I think I see some screws have a minutely longer threaded portion
o Checking the screw gauges will need calipers to be sure but I think some are slimmer
o I'm pretty sure the more petite screws are the Djis, having worked with Djis during the last prop change, specifically shorter thread, smaller gauge