Six men, dressed as builders, bounded three people in their Southall home and "ransacked" the property before stealing the family jewellery.
The men pulled up at the victims' home in Alleyn Park in a white Ford Transit van on June 13 at around 12.10pm.
They got out the back of the vehicle wearing hi-visibility vests and hard hats and burgled the house.
After entering the house, one of the suspects, struck the older male, aged 43 over the head, with what is believed to have been a firearm, before bounding him, a 19-year-old male and a 69-year-old woman.
According to police, the suspects searched the property, ransacked rooms, demanded money and stole all the family jewellery, worth around £14,000, along with a handbag before making off south towards Green Walk.
The older male victim suffered a cut to the head and was treated by the London Ambulance Service at the scene.
The men, five of whom are described as being white and Eastern European while the sixth was black, were all of muscular build.
The Transit van used by the men had a ladder on the roof and a logo on the passenger side door which read Firestone Tires.
Detective Constable Thomas Grimshaw, leading the investigation, said: "This was a terrifying incident in which a family had their home invaded and were then threatened and tied up.
"They have been left traumatised and deprived of valuable jewellery with huge sentimental value. It is imperative that we identify the suspects as soon as possible.
"We have released a picture of the van we believe was used to transport the suspects to the scene. It carries a distinctive 'Firestone Tires' logo and we would ask anyone who has seen this van in their neighbourhood to call police as soon as possible."
Anyone with information about this incident should call the Met’s Flying Squad on 0208 785 8655 or tweet @MetCC.
Crimestoppers can also be contacted anonymously on 0800 555 111.
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