diff --git a/src/classes.py b/src/classes.py
index d42b4ee..02c20d6 100644
--- a/src/classes.py
+++ b/src/classes.py
@@ -14,6 +14,7 @@ class Layer:
     def __init__(self, layer_data):
         try:
             self.extra = layer_data["metadata_decoded"]["extra_fields"]
+            self.layer_number = self.extra["Layer Progressive Number"]["value"] # integer
             self.target_elabid = self.extra["Target"]["value"] # elabid
             self.rheed_system_elabid = self.extra["RHEED System"]["value"] # elabid
             self.laser_system_elabid = self.extra["Laser System"]["value"] # elabid