I don't know; they just showed up at the end of level 23 and after going up to 24.
I got a bracelet with a level 10 Healing Aura on level 24, as well, after taking over the battle tower and picking up the 'Note from Maxos' in the master's chamber (it showed up as one of the quest rewards, so I took it over the gold as my second choice).
After getting into the bunker in the fjords and lowering the barrier, on the third reload with the one-time meeting for the travelling merchant Carleton, I got a couple equipment upgrades and a cleaver with a level 10 Fire Curse enchantment.
Collecting enough zeppelin parts to get to Aleroth (reaching level 25 just before the harbour), I bought a weapon with a level 10 Mana Leech enchantment from one of the merchants there (and three level 8 and 9 potion formula from the other one).
On level 26, just before going up a level, I bought a level 9 Static Charge enchantment formula in Aleroth (second try), and a piece of armour with a level 9 Magic Damage aura enchantment (first try). I wasn't expecting anything from the merchant in Dragon Cliff Castle, but I remembered there were a couple things I wanted to sell that I didn't in Aleroth; he had a necklace with a level 10 Static Charge enchantment.
In High Hall I got something with Retribution Aura 10, and at the harbour a shield with Increase Mana 10. In the bunker I got a shield with a level 10 Magic Protection enchantment, and a bracelet (+8 Dexterity, +2 Poison Arrow, 2 charm slots, 1 enchantment - Magic Damage Aura 10), both on the first try.
