A closer look at this mid-sized, three part, 18KV rated power insulator in dark green, unlisted in GIFONA. The CA designation indicates a wider top cable groove to accomodate larger diameter aluminum wire. (Whoops, I got my mivas and fidenzas confused ;-) Probably a CD 376.X, it is not listed in GIFONA, it measures between the CD 376 and CD 377 dimensu\ional specifications.

This one is slightly larger than a CD 376 (Miva M-315-CA or Fidenza 6315, but not as large as a CD 377

These apparently were marked with A 318 CA and with M 318 CA, IIRC, the "A "designation mens "Alto" or High Vooltage, "M" is for Medium Voltage, and "B" as in BT2CA is for "Basso" or Low Voltage. So the 318 (3 shells, 18KV) may have been consideredas Medium Voltage at one time, and then Alto / High Voltage at a later time.

The dimensions are top skirt: 6 7/8 inch diameter; middle skirt, 5 7/8 diameter; base diameter 4 4/3 inches; and overall height 5 1/2 inches. This matches CD 376 and its derivitavescloser thaneither CD 375 (M 312 CA or 6310) or CD 377 (A 320 CA). As far as I know there is no GIFONA listed CD for the A 318 CA.