The manufacturer identification code (MIC) of your craft identification number (CIN or HIN) is SDG. This MIC (SDG) stands for the company name Sargent's Custom Boats which is currently In Business. This boat manufacturer code has other company names (SDG sometimes goes by these name(s) if applicable: , , , or Steve Bragg & Assoc (oob)). This could happen if the US Coast Guard reissued the MIC to a new company after the first went out of business.
This company (Sargent's Custom Boats) is owned by Joseph M Sargent and is located at 171 N Main St in Milbridge state of Me. It manufactured this vessel and placed your HIN or CIN on the hull. This Boat maker is not owned by a parent company. Sargent's Custom Boats has started making boats, yachts or other watercraft as of 3/20/2017.
More details at the US Coast Guard.
The US Coast guard provides this comment about this watercraft manufacturer: Manufacturer Of Inboard Diesel Cabin Cruisers. Maj.