diff --git a/examples/device_scanner.py b/examples/device_scanner.py
index 8ab61da..78d35bb 100644
--- a/examples/device_scanner.py
+++ b/examples/device_scanner.py
@@ -1,5 +1,8 @@
+from __future__ import annotations
+
 import asyncio
 import logging
+import sys
 
 from findmy import KeyPair
 from findmy.scanner import (
@@ -10,11 +13,6 @@ from findmy.scanner import (
 
 logging.basicConfig(level=logging.INFO)
 
-# Set if you want to check whether a specific key (or accessory!) is in the scan results.
-# Make sure to enter its private key!
-# Leave empty (= None) to not check.
-CHECK_KEY = KeyPair.from_b64("")
-
 
 def _print_nearby(device: NearbyOfflineFindingDevice) -> None:
     print(f"NEARBY Device - {device.mac_address}")
@@ -37,7 +35,7 @@ def _print_separated(device: SeparatedOfflineFindingDevice) -> None:
     print()
 
 
-async def scan() -> None:
+async def scan(check_key: KeyPair | None = None) -> None:
     scanner = await OfflineFindingScanner.create()
 
     print("Scanning for FindMy-devices...")
@@ -55,14 +53,18 @@ async def scan() -> None:
             print()
             continue
 
-        if CHECK_KEY and device.is_from(CHECK_KEY):
+        if check_key and device.is_from(check_key):
             scan_device = device
 
     if scan_device:
         print("Key or accessory was found in scan results! :D")
-    elif CHECK_KEY:
+    elif check_key:
         print("Selected key or accessory was not found in scan results... :c")
 
 
 if __name__ == "__main__":
-    asyncio.run(scan())
+    key = None
+    if len(sys.argv) >= 2:
+        key = KeyPair.from_b64(sys.argv[1])
+
+    asyncio.run(scan(key))
diff --git a/findmy/scanner/scanner.py b/findmy/scanner/scanner.py
index b7e4aa0..af10f12 100644
--- a/findmy/scanner/scanner.py
+++ b/findmy/scanner/scanner.py
@@ -30,13 +30,6 @@ class OfflineFindingDevice(ABC):
     OF_HEADER_SIZE = 2
     OF_TYPE = 0x12
 
-    @classmethod
-    @property
-    @abstractmethod
-    def payload_len(cls) -> int:
-        """Length of OfflineFinding data payload in bytes."""
-        raise NotImplementedError
-
     def __init__(
         self,
         mac_bytes: bytes,
@@ -105,7 +98,11 @@ class OfflineFindingDevice(ABC):
             return None
 
         device_type = next(
-            (dev for dev in cls.__subclasses__() if dev.payload_len == ble_payload[1]),
+            (
+                dev
+                for dev in _DEVICE_TYPES
+                if getattr(dev, "OF_PAYLOAD_LEN", None) == ble_payload[1]
+            ),
             None,
         )
         if device_type is None:
@@ -134,12 +131,7 @@ class OfflineFindingDevice(ABC):
 class NearbyOfflineFindingDevice(OfflineFindingDevice):
     """Offline-Finding device in nearby state."""
 
-    @classmethod
-    @property
-    @override
-    def payload_len(cls) -> int:
-        """Length of OfflineFinding data payload in bytes."""
-        return 0x02  # 2
+    OF_PAYLOAD_LEN = 0x02  # 2
 
     def __init__(
         self,
@@ -180,7 +172,7 @@ class NearbyOfflineFindingDevice(OfflineFindingDevice):
         additional_data: dict[Any, Any] | None = None,
     ) -> NearbyOfflineFindingDevice | None:
         """Get a NearbyOfflineFindingDevice object from an OF message payload."""
-        if len(payload) != cls.payload_len:
+        if len(payload) != cls.OF_PAYLOAD_LEN:
             logger.error(
                 "Invalid OF data length: %s instead of %s",
                 len(payload),
@@ -208,12 +200,7 @@ class NearbyOfflineFindingDevice(OfflineFindingDevice):
 class SeparatedOfflineFindingDevice(OfflineFindingDevice, HasPublicKey):
     """Offline-Finding device in separated state."""
 
-    @classmethod
-    @property
-    @override
-    def payload_len(cls) -> int:
-        """Length of OfflineFinding data in bytes."""
-        return 0x19  # 25
+    OF_PAYLOAD_LEN = 0x19  # 25
 
     def __init__(  # noqa: PLR0913
         self,
@@ -267,7 +254,7 @@ class SeparatedOfflineFindingDevice(OfflineFindingDevice, HasPublicKey):
         additional_data: dict[Any, Any] | None = None,
     ) -> SeparatedOfflineFindingDevice | None:
         """Get a SeparatedOfflineFindingDevice object from an OF message payload."""
-        if len(payload) != cls.payload_len:
+        if len(payload) != cls.OF_PAYLOAD_LEN:
             logger.error(
                 "Invalid OF data length: %s instead of %s",
                 len(payload),
@@ -306,6 +293,12 @@ class SeparatedOfflineFindingDevice(OfflineFindingDevice, HasPublicKey):
         )
 
 
+_DEVICE_TYPES = {
+    NearbyOfflineFindingDevice,
+    SeparatedOfflineFindingDevice,
+}
+
+
 class OfflineFindingScanner:
     """BLE scanner that searches for `OfflineFindingDevice`s."""