[cctalk] Dysan 208-21 alignment disk - what is it for?

Hi there, Does anyone have the spec sheet for the Dysan 208-21 alignment disk, or know what drive it's intended to be used with? I've got the information sheet which comes with the disk, but it doesn't identify the tracks-per-inch or track count. It's a 5.25in double-sided disk; the info sheet says: FILE: 208-21 PAGE 001 Dysan 208-21 (Configuration #802030) Double Sided Alignment Diskette Track 0 - Full Revolution (both sides) Track 1 - Index Burst (both sides) Track 16 - Index, Azimuth and Catseye (both sides) Track 33 - Full Revolution (both sides) Track 34 - Index and Azimuth (both sides) Full Revolution - recording frequency is 125 kHz Index Burst - 50us in duration and occurs 200us after index. Recording frequency 125 kHz. Azimuth - Four bursts that depicts an azimuth of 12'. Each burst is 1 millisecond in duration with the first burst occurring 500us after index. The recording frequency is 125kHz. Catseye - recording frequency 62.5 kHz Sadly the part number doesn't appear on Accurite's old website (per archive.org), or the Dysan PDFs I've found on Bitsavers. About the only thing I've been able to figure out is that it's an Analog Alignment Disk. Thanks, -- Phil. classiccmp(a)philpem.me.uk https://www.philpem.me.uk/