Variable Capacitor Pfd

Hello: I'm currently accumulating parts for a magnetic loop receiving antenna. I'm going to use 3/4" copper tbg. My feed ring will be 1/5th the size of the 30"diameter main loop. Anyway, I picked up an old metal and ceramic 18 bladed variable capacitor--18 blades on each side (total 36); it's about 3" in length and has a ball-bearing shaft. When the capacitor is fully disengaged ea. blade is spaced 1/8th" inch from the next blade, and I'm wondering how many Pfd it "might" be. I'm not fussy at this point; but I'd like about 385Pfd or better. What's the easiest way to determine its Pfd? I'd like to link a close-up photo of the old fellow, as well as that of an interesting older radio chasis that I bought (for anyone's perusal and identification). Is it possible to post or link a photo on this forum? It would be so much better than a description. I s'pose not. My apologies, I'm quite new to all of this. Thank you!