The SC220 is a general purpose industrial telephone, to be used in wet and salty areas.
It is type approved by DNV-GL for maritime use. 
Full data sheet, mechanical drawing and manual can be found here:  SC220 data

Specifications:​

• 2 wire analogue telephone
• DTMF dialing
• 50V AC ringing
• 600 ohm line impedance
• Connects handset
• Connects headset
• Relay for driving external flash / horn
• Water tight enclosure (IP65 with optional front cover)
• Full numeric keyboard with R function
• Headset button for use when handset is not used
• MIC button for PTT mode with handset
• Busy tone disconnect function
• Programmable gain and volume
• Type approved by DNV-GL

Interfaces:

• 2 wire telephne line
• Handset
• ​Headset
• Relay for driving flash/horn