SCHENECTADY — Sunlight on the blue stone wall of the Front Street Victorian house gave Don Rittner a sudden insight.

The city historian was strolling through the historic Stockade neighborhood two years ago when he noticed the stonework through a narrow gap between buildings. Rittner then recalled a statement from 19th century city historian Jonathan Pearson: There are no stone houses in Schenectady.

“I sort of did a double-take,” he recalled Tuesday.

Rittner now believes the stucco facade of Daniel Partington and Sharon Cole’s home is concealing a former British Army blockhouse that could be among the oldest structures in the county. And his work has caught the attention of a nationally syndicated program exploring extraordinary objects in everyday homes.

This summer, the Public Broadcasting Service will feature the home at 9 Front St. during the sixth season of the show “History Detectives.” Film crews began shooting the episode this week and will conclude this afternoon at the house near the Washington Avenue intersection.

Partington and Cole were originally told the building dated back to the 1890s, making it relatively young by Stockade standards. Some date to the 18th century. But the couple began to question the true age of their home after making a few peculiar discoveries.

Partington noticed the hand-hewn hemlock beams in the house’s basement and stonework that extended from the foundation to the attic, where he found newspapers from the early 1820s wedged between the rocks. He also noticed a discrepancy between the width of exterior walls, which measure more than 2 feet thick in a 24-by-24-foot area of the house.

That definitely raised his suspicions, he said.

MAP HISTORY

Meanwhile, Rittner’s research led him to an 18th century French map of Schenectady, which placed a wooden blockhouse several hundred yards away from the stone Front Street building. He said it seemed only natural that another would be built nearby and overlooking the Mohawk River.

Blockhouses were constructed by the British to fortify the ever-growing village against persistent Indian attacks. The two-story square structures once anchored the four corners of the stockade and were manned by soldiers.

Rittner said homes built inside the stockade seldom included any stonework due to the scarcity of rock in the area. For this reason, he said stone was almost exclusively reserved for military fortifications, which makes Partington and Cole’s home an intriguing find.

An addition was built on the rear of the home and its exterior was almost completely covered with stucco, giving it a distinctly Victorian appearance. Rittner said the only thing that prevented the building’s stonework exterior from being completely obscured was the small, foot-wide space between the couple’s house and the building next door, which apparently prevented workers from applying the stucco.

“You’ve heard the old saying ‘don’t judge a book by its cover,’ ” he said. “Well, don’t judge a building by its facade.”

Last fall, researchers from Cornell University took samples from the basement and attic beams. By studying the borings, Rittner said, historians will be able to determine the age of the beams down to the year.

“This may be the oldest structure in Schenectady,” he said.

With a good amount of circumstantial evidence already existing, PBS producers decided that the blockhouse possibility was enough to feature on “History Detectives.” Elyse Luray, one of four hosts on the show, spent two days reviewing Rittner’s work and examining the house for a 20-minute segment on the show.

Luray said the program will explore the fur trade along the Mohawk River, along with the struggles of early Colonial traders on the untamed frontier. She said the house could prove to be one of the few remaining from when British and Dutch traders maintained a very tentative foothold in the area.

“When this airs, the rest of the country will know that Schenectady was one of the first American frontiers,” she said. “You never know what you’ll find in your attic.”