We are so used to small, slick smartphones which can do just about anything, it's easy to forget that the mobile phone was once very different.
The old-school, "water bottle" phones may have been clunky, but they did have their advantages. Writer and actor Michael Hui demonstrated this in the classic 1989 film Mr Coconut, when his character knocked down a runaway thief by throwing a hefty phone at him.
But for Spandau Tam Wai-yip, old mobile phones aren't just lethal weapons. He's been collecting them for almost 20 years.
"These phones can still cost up to HK$20,000 to HK$30,000, even if it has a black and white monitor and can only dial in and out," he says.
Tam fell in love with mobile phones after buying his first model, an Ericsson 337, in 1995.
These early mobile phones look nothing like modern smartphones, but Tam still appreciates them.
Unlike most Hongkongers who are keen to chase the latest models, he is far more interested in the classics. While people are lining up outside shops to purchase new releases, Tam enjoys hunting for old phones in stores on Apliu Street in Sham Shui Po.
"I am only into old models so there's very little competition. Many of my phones are considered junk by others. Now I have more than 400 of them," he says.
Storing such a large number of phones isn't easy. To ensure the phones keep working, Tam stores each phone separately from its battery.
"The battery will spoil after a few years, so to preserve the phone I keep them separate," he says.
"All of my phones are functional, but some can no longer be turned on because I can't replace their battery."
Tam says he's drawn to old mobile phones because of their unique, creative designs.
"There are slide phones, folding phones - they come in various shapes. There are no surprises in the design of smartphones [today]. They all look the same, with a rectangular screen."
Mobile phones used to be treasured possessions that would last for years, says Tam.
But now you are likely to discard your smartphone for a newer model in a matter of months.
"Designers used to put a lot of effort into the design as phones were on sale for at least a year. Now there are new models every few months. I don't think this helps to produce high-quality phones," he says.
While Tam estimates that his collection of phones is worth more than HK$500,000, he isn't in it for the money.
"The phones contain my memories. When I look at a phone, I think of the life I had when I was using that phone. It is actually a really comforting feeling," he says.
"It makes me happy to hear visitors at exhibitions sharing their life experiences while looking at old phones. The phones bring back good memories for many people."
The vintage mobile phones exhibition at Pioneer Centre in Mong Kok showcases more than 600 phones dating back to the 1990s. It runs until August 31