Product description   
1.4 External design of the device 
  SIMATIC IPC BX-39A 
14  Operating Instructions, 07/2022, A5E50715883-AA 
⑪  Opening for expansion 
Interfaces of external expansion modules (M.2 format) 
Status display of the operating state 
 
Device with expansion slots 
Other device variants (Page 43): 
•  with slot for one PCIe expansion card 
•  with slots for two PCIe expansion cards 
You can find more information about expansion cards under "Expansion cards (Page 57)".