Allen Chung, 73, thumbs a rectangular plastic piece bearing the unit number of his old home. He pierces the nostalgia-filled moment with an abrupt admission, a mischievous glint in his eyes. “We actually took this without permission,” he said. His 71-year-old wife Ann, a retired teacher, smiles sheepishly next to him. For 30 years, the unit number adorned the entrance of their 1,600 sq ft family home in Shunfu Ville. The condominium, located in a central suburban neighbourhood, was sold…