In the late days of steam we see an ex M-1 tender used as an auxiliary tank on an L-1. (Pix Classic Trains Vol III, pg 44).
1.When such tanks were used were the coal bunkers emptied of coal?
2. Were the bunkers fitted with a water tank?
3. How were the tanks/tenders numerically identified... With the donor loco's number, totally new number or what?