This appears to be a customized HP RP9 Model 918G1 All-in-One POS System.
Key specifications would be dependent on the specific customization options selected when ordering (e.g., processor, memory, storage, display, peripherals). Without knowing the specific build sheet, it is impossible to provide definitive specifications.
Typical RP9 G1 specifications include:
Processor: Intel Celeron, Pentium, or Core i Series (6th Gen)