A 173-year-old time capsule and granite foundation stone of the country's oldest Catholic church have been unearthed, in what experts describe as a "rare discovery".

Contractors found the hitherto missing capsule and foundation stone earlier this year while restoring the Cathedral of the Good Shepherd along Queen Street.

The time capsule - possibly the oldest one found here - comprises publications such as a prayer booklet and newspapers from 1843, as well as 24 international 18th- and 19th-century coins and tokens. A foundation stone, or cornerstone, is the first stone set in the construction of a masonry foundation.

Mr Ho Weng Hin of Studio Lapis, the cathedral's conservation specialist consultant, said both artefacts mark the times in which they were constructed and embody the values the community held dear.

They were buried by one of Singapore's early founding communities - French Catholic missionary priests of the church, among others.

Highlighting the significance of the find, archaeologist Lim Chen Sian said: "A church being erected in the mid-19th century was a major event for the nascent European community... Remember, it was just about 24 years since Singapore's founding."

It was also one of the largest and most monumental buildings of its time, experts said.

The church was conferred the status of a cathedral - the seat of a bishop - later in 1888. It was gazetted as a national monument in 1973.

The time capsule pit, about the size of a shoe box, was found under a column base on a series of granite steps along the cathedral's Victoria Street facade on Jan 29. It had been sealed shut by the foundation stone.

The currencies from places such as Vietnam, Britain, France, Spain, and the British East India Company drive home the point that Singapore was an important place for trade, said Mr Ho.

Mr Lim believes the multinational collection of coins was perhaps an attempt to "heal and marry the schism" which existed between the early Catholic orders of varied nationalities such as the French, Portuguese and Spanish, that were present in early Singapore.

The present-day find corroborates a June 22, 1843 news report in the Singapore Free Press, which said the church's foundation stone was laid above the pit in an early morning procession on June 18 that year.

While the Singapore Free Press report specified that the stone was laid on the front corner of the church, historians had assumed that its original frontage faced Queen Street.

Contractors had been asked to look out for the missing capsule around the site during restoration, said the cathedral's technical committee secretary Jevon Liew.

Cathedral rector, Monsignor Philip Heng, told The Straits Times the find illustrates that the Catholic community here foresaw its own longevity. "The founders realised that, one day, someone was going to be digging and would see that they had anticipated and had hope that the Catholic community would still be in existence in Singapore centuries later," he said.

Contractors chanced upon the artefacts after a pediment below the cathedral's bell tower collapsed on Sept 3 last year. Seven of the eight brick columns that held up this pediment along Victoria Street also collapsed.

While the pediment and columns will be reconstructed, Mr Ho proposed saving two of them for future display in some form on the cathedral's grounds. As workers were removing one of the two columns, they found the various artefacts scattered alongside two broken apothecary bottles in the rubble-filled pit.

The approximately A3-sized cornerstone formed part of one of the column bases. The time capsule was also reported to have comprised publications such as a prayer and ceremonies booklet from the first service at the new site, and 1843 editions of the Singapore Free Press, the Straits Messenger, the Bengal Catholic Herald and the Madras Catholic Expositor.

The publications were found in varying states of decay. According to old reports, they had been placed in vases beneath the cornerstone - likely the apothecary bottles discovered by workers.

Mr Ho believes that the newspapers could have been included to impress on future generations that the community had been civilised and cultured. He said the inclusion of the religious publications was to show the link between Singapore's Catholic community and the international one.

Monsignor Heng added that the construction of the church had been a milestone for the Catholic community.

He said the plan now is to restore the artefacts and display them in the cathedral's new heritage gallery when the institution reopens. Its official reopening has been set tentatively for next February. The $38 million restoration project, which started in November 2013, was delayed by about five months by the collapse of the columns.

Archaeologist Mr Lim, who had conducted an archaeological dig outside the priests' residence in 2013, will be studying the finds and incorporating his analysis as part of the cathedral's heritage gallery.

Monsignor Heng said there are also plans for a new commemorative stone to be inserted into the restored structure.

He said: "Like our predecessors, we too are anticipating future generations to enjoy the cathedral."