Audio Technica AT677 Aluminum Alloy Turntable Platter Mat. These are very hard to come by and this one is in excellent condition.

Description:

1.5 "tapered aluminum alloy plate.
Manufacturer: audio-technica
Model name: AT677
Dimensions: Diameter 289mm x Thickness 7mm
Weight: 980g
Material: Technihard material with hard sapphire crystal growth coating

From the Japanese Translation:

This is a superb Audio-Technica AT677 Audiophile turntable matt made out of Technihard aluminum used by NASA in space program.

The AT 677 is designed to trace the groove on the vinyl to the last detail. The surface is recurved 1.5 degree from the periphery of the disc towards the center, which makes the record surface closely fit to it using a stabilizer (more than 400g is recommended). This corrects the warpage of an analog record and makes the stylus-moving stable

The inner peripheral side is 4.5 mm and outer peripheral side 7mm. Weight of the disc is 980 gr.

There are sufficient effects when used alone on the flat side without writing, but it should be used in conjunction with record stabilizer to get the best out of it.

Heavy aluminum alloy surface has a coat of sapphire crystal, preventing static, significant reduction of vibration and providing a right angle for the needle, reading the optimal amount of information from the record.

Thanks for looking.