This regulator first stage seems to be in very good condition.  I believe it is the model called The Oasis.  I put a second stage on it and plugged the other open ports and put it on a full tank.  It worked fine, but, as with any "life-support" equipment, have it checked out by a Sherwood Authorized repair facility before you take it diving.  I used a small flashlight to look into the open ports.  There are no signs of oxidation on the parts I could see.  The filter is also perfectly clean.  The small dot-matrix model number on the body of the regulator looks like SRB5700, but it is difficult to read and I may have not read the last two numbers correctly.   This first stage is designed with two high pressure ports and four low pressure ports.  Two of the LP ports are marked PRI for primary.  These would be used for your second stages.  The other LP ports would be used for your BC inflator hose and a drysuit inflator hose, if you had one.  

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