It looks as if the shelves are metal with a glass top suspended on a bumper of sorts. I would think that both the metal and glass would ring, and a bit more than a polymer bumper could neutralise.
Bruce
Theories are not so much answers as questions, to be supported or undermined by experience & testing.
Source: Audiolab 6000CDT > Calyx 24/192 DAC
Amplification: Pass-design B1rev2 pre-amplifier > Neurochrome Modulus 686.
Loudspeakers: Proac Response 1SC
Cables/stands: spkr: MIT MH-750 biwire; IC: HT Truthlink; Target stands, sand-filled; Excel Cat6A 23AWG UFTP & 1attack.de Cat.7 SFTP.
Other: Balanced AC transformer to hydra mains distr; Bass traps & Acoustic panels; Isolation: Inner tube & roller bearings; 3xZyxel ES104A switches in series w/Vreg upgrades.