From the code on the frame it is a 1984. I have a couple of 1984 Basso Gap frames (numbers 402153 and 405145) as verified from Basso. The first number corresponds to the year of manufacture in the 1980's. Also, somewhere around 1983-1984 the cable guides moved under the bottom bracket.

Both my frames are single bottle mounts and no pump peg as shown on yours.

Also, yours has a full chrome front fork whereas on mine and others I have seen only the unicrown and dropouts are chromed, the remainder of the fork painted to match the frame color.

Interestingly, there seems to be wild variations in the frames they churned out then. Some non-standard colors and frames. For instance, one of my frames is a non-standard metallic black and lighter than the other by a couple of ounces.

One of my bottom brackets (the heavier italian blue frame) is solid, whereas the metallic black one is slotted like yours. Unfortunately, I don't seem to be able to find the bare frame weights at this time.

I'd disassemble the bike, TLC the bearings, and spray some frame saver inside the frame and fork to be safe.