1970s Hubcap lock troubleshooting

[TNdeville]

I'm a new owner of a 1970 deville with locking wire hubcaps, I believe to be from a later year.  Car did not include the key.  Each cap has 2 locks opposite (9 and 3 o'clock).  4 leaf clover shape.  I bought a key that fits, but they won't budge and I'm afraid I'll strip the key.  I have read each lock is a hook that rotates 1/4 turn to attach to the rim.  I have seen pictures online of the mechanism.

I've tried multiple sprays of penetrating oil, they stay stuck with no improvement.  Locks are too deep to reach and slit with a dremel.

I've considered brute force with a pry bar and/or drilling them out, but would rather not damage the caps.

Anyone have experience with these locks?
Are they a prized hubcap?
If I am able to remove the lock/hook mechanism, will the caps still be usable?

I have attached photos of my hubcap, the lock, and the key I purchased.

Thank you all, this is my first post. 

T Clark

[TJ Hopland]

Its a 1/4 turn because its basically a hook that goes through the small slots in the rim between the rim part and the spider web hub center section.  There are no threads its got washers and a spring that keeps tension.  I think one of the washers kinda rode on a cam and had a tab that kinda gave it a detente.  That cam thing is also supposed to limit the range to that 1/4 turn but people force it past that and that plus some time seems to be what gets em stuck. 

Maybe have a look from the back around rotors and drums to see if you can possibly see the hook ends to know which way to turn them?  Or possibly get in from that direction to pry at or try and twist the hooks?  Forcing and prying from the back won't damage the rest of the cap.  If you are trying to pry the cap off with them locked that will for sure do some damage to the overall cap.   I had a 78 where some were damaged when I got it and I didn't have issues with the caps staying on without the locks.

I think those caps are 77-79 ish.  Wait till you get them off you will be amazed at how heavy they are.  They spent a gizillion dollars shaving like 100 pounds off the 425 engine then put it right back on the car with those caps.    80's they went to a design where there is a 3 legged frame that goes over 3 of the lug nuts and this frame either has a stud or a threaded hole that accepts the keyed locking bolt or nut that is hidden by the little center cap or crest.