Either the Baltimore Sun is very astute in its observation of the changes in business development and relationships in the region, or 10 Washington-area companies moved to Baltimore last week in a mass relocation of corporate headquarters.

But those same 10 companies were still doing business at their old corporate addresses in metropolitan Washington yesterday morning, just as they were Wednesday when The Sun identified them as local (Maryland) firms.

The Sun ran a list of 56 companies, showing the performance of their stocks in the over-the-counter market during the first six months of 1983. The performance chart of so-called local OTC issues was provided by the National Association of Securities Dealers at the request of The Sun's business editor, Philip Moeller.

The Nasdaq list contains some eye-popping figures representing percentage increases in the market values of several issues, most notably a 345 percent jump for Dart Drug Corp. But Dart and three other companies on the list are based in Landover, just outside the District. Some others on the list have corporate addresses in the District and suburban locations that include Bethesda, Rockville and Lanham.

The corporate addresses of companies on the list were of no great siginificance as far as he was concerned, Moeller explained. "We're interested in companies based in Maryland," he said. "I hate to get into these debates about where companies are located."

In that sense, The Sun's view of business in the Washington-Baltimore corridor coincides with that expressed by The Post in May when it published a list of the Top 100+ companies in the area. Although some of those companies clearly aren't based in the District, they are regional firms with which Washington-area residents are likely to be affiliated through investments, employment or as consumers, The Post noted.

The conclusion seems fairly obvious when the facts are considered objectively: Demographic changes, expanded markets and shifts in the economy have forged stronger regional identities for many companies along the Baltimore-Washington axis.

Indeed, by expanding to meet demands of a growing market--the fourth largest in the United States--many Washington and Baltimore companies have all but made geographic boundaries moot. Only political jurisdictions separate consumers in the region.

That was the point of an earlier Capital Commerce column that sparked a stinging response from the Sun's sister publication, The Evening Sun. In an earlier column, The Evening Sun equated publication of the Top 100+ with Washington's annexation of Baltimore.

"The last time I looked, all those firms were in and around Baltimore," The Evening Sun griped about including some Baltimore-area firms in the Top 100+ list.

In addition to Dart Drug Corp., The Sun's OTC list includes unmistakably Washington-area companies such as Trak Auto Corp., Greater Washington Investors Inc., Hechinger Co., Suburban Bancorp, and Schwartz Brothers. The last time I looked, all those companies were in and around Washington.

But that's relatively unimportant to investors and consumers. As The Evening Sun so aptly put it after receiving a complaint from the Washington Baltimore Regional Association, "together Washington and Baltimore form a massive, wealthy and growing economic unit."

And now that another Baltimore paper has seen fit to publish a list of "local" companies, some of them 40 miles away, the concept of a common market, so ardently advocated by business leaders in the region, takes on added credibility.

By handling the OTC list as it did, The Sun also gives added emphasis to a truism expressed some time ago by the WBRA when it observed that "regionalism has come of age" and that it is "a new economic factor in America."