With very few exceptions, I recall just about everything, including dragon hoard loot, being fully tradable. I realize that this probably happened progressively, but I'm wondering about what point free trading was killed on normal servers?
The first 3 expansions all have a mix of tradeable/no trade raid loot. Planar items were no trade while Dragons/Yael were tradeable. Kunark is fully tradeable outside of a couple items from VS and all of VP. Velious has a mix with Dragon loot outside of TOV and Dain / KD being tradeable with some no trade TOV is all No Trade Tunare/Growth is all No Trade Sleepers Tomb is all No Trade With raid loot - Luclin was fully no drop raid loot as far as I can recall. Even trash raid mobs like Grieg/Servitor/UP raid mobs/THO are no trade items. As far as I know they finally minimalized/killed off group loot trade in OoW with the advent of the attuneable tag in an effort to emulate WoW. The effort was to reduce items being recycled on the market as a counter to making items more common. I don't play beyond that really. When I did explore TSS and beyond it was on FV server so i don't know what is actually tradeable vs not on a normal server.
I started playing the first week of launch March 1999. The No Drop progression started a month or two after launch. One of the first I saw changed were Gnoll Teeth out of Blackburrow. Use to sell those for 1 plat each. Then much later they started introducing Lore Items to hinder the farmers.
Seru's drops were definitely all NO DROP. I think you may be able to turn in the horse for plat in Bazaar? Not sure, rest is definitely not tradeable, not the ancient spells and neither of his drops