If June resale house prices in Montgomery County are an accurate bellwether of the area realty market, the upward boom may have peaked. At any rate, appraiser Alfred Jarchow's analysis of multiple listing sales in June showed the median price of resale houses to be $63,000, some $3,000 less than the high median in May. However, June prices averaged 8.8 per cent above the level of resale prices in the same month in 1976. Also significant in the Jarchow report, which be notes are based on incomplete returns, is the June sales volume of existing house will equal about 22 per cent of the active listings of houses for sale. That fact and a look at the apartments offered for rent in the classified ad sections hardly supports a view that this area has a housing shortage.

Newly on board as the executive vice president of the Routh Robbins real estate firm in this area. Robert Rathbun has come east from the California offices of the Forrest Olsen firm, also a part of the Coldwell Banker realty conglomerate. Donald E. McNary said he is staying on as president of the firm that now has 14 area offices and is expected to shoot for 25 under Rathbun's California-style leadership . . . Routh Robbins, founder of the firm that was the area's largest in the late 1960s, is reported still seriously ill at her daughter's farm in rural Virginia. The Robbins firm was sold to Cold well Banker about 19 months ago.

Realtor Caroline Campbell, whose unobtrusive business address is up the road a piece from the restored mill visible from Route 7 in the Great Falls area, is marking her 30th year in real estate and happy about almost everything except "too many listings" on the market. But the firm recently found a buyer for a contemporary house on 6 acres in the Cornwall Farms area. Built by Bill Blatz for his own occupancy, the house will be sold to Raymond and Sophia Ethier for about $285,000. What's unusual about the house? For starters, it has a master bedroom that occupies the entire second floor. And the master bath is one of those sunken Roman jobbies that seem to turn up so often these days in upper priced dwellings.