A Completely New Type of Magic Item? You tell me!

So here are two examples of what I think maybe a completely new magical item type for the OSR. Of course, there's more than a decent chance that I'm wrong (I'm far from uber-literate regarding all OSR rpgs) and I'd love to know if something like this has been done before.

Behold the first (?) Transmutational Magic Items, magic items that alter a character's magic during the casting!

Apprentice Wand: Traditionally given by a master to his former student on the last day of his apprenticeship, the apprentice wand is typically straight yew tipped with brass. When a charge is used, it transforms any 1st-level spell into a read magic spell. It can be recharged by casting read magic spells upon it. Experience Point Value: 250 G. P. Value: 500.

Staff of the Thistle: Formed from the root of a bramble bush, the staff of the thistle has the following transmutational magic functions when a charge is used:

1. Grasping Thistle: Upon the casting of any 2nd-level druidic spell, the staff transmutes the spell into an entangle, but all entangling plants also grow spikes, inflicting 1-2 hit points of damage per round spent in the area of effect, regardless if a creature is entangled.

2. Spiny Grass: Upon the casting of entangle, the staff transmutes the spell into spiny grass in an area of effect that is double the entangle.  The area is considered covered with caltrops for the duration of the spell. For each yard traveled in the area, a creature is attacked by a 1+1HD creature and any hit has a 25% chance to slow movement by 25% for the next 4 days. If a creature is hit a number of times equal to its feet (two for bipeds, four for horses, etc.) the creature’s movement is reduced by 90% for the next 8 days.

A staff of the thistle can be recharged by casting plant growth upon it. Experience Point Value: 750 G. P. Value: 5,000.