Sure! Below is a test case generator for the problem statement "Old Bridges" described above:

```python
import random

def tcgen():
    datasets = []
    
    while True:
        # Generate a random number of islands n
        n = random.randint(1, 25)
        
        # Generate the treasures and bridge limits for each island
        islands_info = []
        for _ in range(n):
            treasure = random.randint(1, 50)  # Assuming treasure amount can be between 1 and 50 for variability
            max_bridge_load = random.randint(treasure, 100)  # Ensuring max_bridge_load >= treasure for feasibility
            islands_info.append((treasure, max_bridge_load))
        
        # Add the dataset to the list
        datasets.append((n, islands_info))
        
        # Break loop randomly to simulate multiple datasets, ensuring there is at least one dataset
        if random.choice([True, False]) and len(datasets) > 1:
            break
    
    # Add the terminating dataset (n=0)
    datasets.append((0, []))
    
    return datasets

# Example usage
if __name__ == "__main__":
    datasets = tcgen()
    for dataset in datasets:
        n, islands_info = dataset
        if n == 0:
            print(n)
        else:
            print(n)
            for treasure, max_bridge_load in islands_info:
                print(treasure, max_bridge_load)
```

### Explanation
1. **Random Dataset Generation**:
   - A random number of islands `n` (1 ≤ `n` ≤ 25) is generated.
   - For each island, a random amount of treasures and a maximum bridge load are generated. The maximum bridge load is ensured to be at least as large as the treasure amount to have valid test cases.

2. **Multiple Datasets**:
   - Multiple datasets are generated until a random choice decides to stop, ensuring there is at least one valid dataset.
   
3. **Terminating Dataset**:
   - Finally, a terminating dataset with `n = 0` is added to signify the end of input.

4. **Output Format**:
   - The generated datasets are printed in the specified format.

This test case generator ensures a variety of input scenarios which can be used to thoroughly test the solution for the "Old Bridges" problem.