The Grulla you have is a 7 pin sidelock. The new ones are only 5 pin locks.
The new ones have less complicated locks, prettier wood, better fit and finish.
The old ones have rougher internal fit and finish, better locks, only moderate quality wood.
Those that are neither new nor old (appx. 1988-1995) are the worst, the DIARM era ones that are not at all desirable. Blue book on those interim era ones are quite prejudicial, perhaps $800-$1000.
Single trigger Spanish guns are extremely prone to flaws and are to be avoided like the plague. Even if you have a good one, a negative price/value is assigned to your gun because of the stigma associated with Basque trigger timing skills.
