As you continue your adventure through Resident Evil Village, you will come across many items and treasures. Some of them are combinable, including Heisenberg's Hammer.
First mechanical part
You will naturally stumble upon this part once you reach level -1 of the Factory.
Second mechanical part
To find the second mechanical part, you will have to go to floor -4B to find the Heisenberg's Quarters. To open the door of the room that holds the other part of the treasure, you will have to make Heisenberg's key. The foundry is located right next door.
You now just have to combine the parts to get Heisenberg's Hammer. It's a valuable you can sell to the Duke.
You'll need a key to be able to enter the Heisenberg Factory and continue your adventure in Resident Evil Village. Here's a guide on how to get the key to Heisenberg.