Siemens SIMATIC SM 335 Manual page 14

Characteristics and Technical Specifications of the SM 335
Revision Level
Products with the same number can be distinguished by the revision level.
The revision level is incremented by upwardly-compatible function expansions or
fault corrections.
The revision level of the module is identified by "X" (see Figure 1-1); in this case
the revision level is 1.
1-4
SM 335 – High-Speed Analog Input/Output Module for the SIMATIC S7-300
6ES7 335-7HG00-8BA1