```python
from typing import List, Dict, Union

def field_mean(records: List[Dict[str, Union[int, float]]], field: str) -> int:
    if not records:
        return 0
    
    total_sum = 0
    count = 0
    for record in records:
        if field in record and isinstance(record[field], (int, float)):
            total_sum += record[field]
            count += 1
    
    if count == 0:
        return 0
    
    return int(total_sum // count)
```