At the start of January, he held 14.7% of the Stirling business but sold 2.6 million shares to reduce his holding to 9.4%.
The sale of a further 850,000 shares eroded his holding to 7.7%
Yesterday, a stock market announcement confirmed that Mr Gyllenhammar's Union Discount Company of London had reduced its stake to less than 3%.
Superglass shares closed the day unchanged at 5.52p.
It reported flat revenue in the 12 months to August 31, and narrowed operating losses from £4.3 million to £2.5m.
The company is implementing a major turnaround plan to shave around £1.4m in costs.