SAN JOSE — A housing high-rise’s owner has just launched sales for the top-floor penthouses in the San Jose tower, an effort that arrives at a time when the building has reached a marketing milestone.

The latest sales endeavor is focused on the four penthouses in one of the two housing towers at 188 West St. James St., whose occupancy is deemed to be a key piece in efforts to bring new life to downtown San Jose.

Machine Investment Group gained ownership of the two towers near San Pedro Square through a speedy foreclosure process that valued the residential hub at $181.9 million.

Starting in mid-May, Machine Investment and property operator Centurion Real Estate Partners began marketing non-penthouse units. Machine has reached a milestone of 20 completed sales.

The penthouses are now becoming a major focus for Machine and Centurion.

“These are our trophy units,” said John Tashjian, managing partner with Centurion. The penthouses all have floor-to-ceiling windows with wide-ranging views of the Santa Clara Valley and its adjacent mountains.

Prices for the four penthouses range from $1.88 million to more than $3.6 million, according to Centurion. The penthouses are two- or three-bedroom units. Sizes range from 1,581 to 3,002 square feet.

The double-tower housing hub consists of a 22-story eastern tower with 337 units and a 20-story western tower with 303 units. The sales efforts are focused solely in the western tower.

The residential complex is deemed to be a key cog in San Jose’s quest to infuse its sluggish urban core with more activity and foot traffic.

China-based Z&L Properties developed the high-rises, then wound up presiding over a financial, construction, development and legal ordeal that engulfed the towers over an eight-year stretch.

The problems were severe enough that a Z&L affiliate was forced to cede ownership of the property through the foreclosure.

“Downtown San Jose has been waiting for years for the increased foot traffic that 188 West St. James was supposed to bring,” said Bob Staedler, principal executive with Silicon Valley Synergy, a land-use consultancy.

Instead, until this year, the two towers, which together totaled 640 units that could potentially accommodate 1,000 residents, remained nearly dormant.

“The delays and slow sales have had a real impact on nearby businesses and restaurants that were counting on hundreds of new residents in the neighborhood,” Staedler said.

Centurion and Machine began seeking buyers for the non-penthouse units in the western tower during the spring, with the first purchase taking place in May.

The owner officially completed the 20 sales, as of Sept. 30, at an average price of just over $726,600 per condo, a review of the recorded transactions on file in Santa Clara County shows.

Four of the sales of the non-penthouse units topped $1 million, according to the county’s real estate records. Fourteen units fetched prices that ranged from $500,000 to just under $1 million. Two units were completed at prices in the $400,000s.

The highest recorded price occurred in July, when one of the condos was bought for about $1.27 million.

During the early months of this year, the Machine firm invested $30 million to revamp and upgrade the towers, common areas and amenities ahead of the condo sales.

The owner and operator redesigned the lobbies and launched a third-floor club whose features include private workspaces, social lounges, a catering kitchen, an outdoor terrace, a 75-foot pool, a hot tub and barbecue areas.

frenchCALIFORNIA designed the interior of one penthouse, architect Steinberg Hart led the design of the reimagined lobby, and C2K Architecture provided the overall design of the two housing towers.

With the amenities in place, Machine Investment and Centurion Real Estate are seeing heightened enthusiasm from existing owners and prospective residents.

“People see the property turning the corner; they see the upgrades in the amenities spaces and they see value in getting in on this,” Tashjian said.