Graham Guthrie and his wife are unhappy about lock boxes - small metal boxes real estate agents sometimes attach to the front doors of houses they are showing. Qualified agents have common keys to all lock boxes and thus can enter a house and show it to a prospect when the owner is away. Mrs. Guthrie says she was away from her north Arlington house, which was on the market for $200,000, only five hours Feb. 2. The next day she discovered that an estimated $5,000 in silver and a fur cape were missing. She said Arlington police investigated and found no sign of forced entry. Trusted workmen who were at the next-door site of a new house being built for the Guthries said they noticed a well-dressed man enter the house twice during the time Mrs. Guthrie was absent. In December, James Moriarty and his wife reported that $1,800 worth of jewelry was taken from their home on which a lock box had been appended. Generally, area real estate board and realtors using lock boxes have expressed confidence in the security of the system.

A commercial building at 1010 16th St. NW was sold recenty for $590,000 by L. M. Milstone and others to Mr. and Mrs. Reuben Tebeleff.

Recently, the sewer service charge in Fairfax County was raised to $1.41 per thousand gallons - a sizable boost from the former charge of 95 cents per thousand. The average family in the county is billed for sewer service on the basis of 88,000 gallons a year. But more important to new home buyers and builders will be the raise in the sewer availability charge to $1,500 from $1,000. Effectively, that will add $500 to the cost of each new house and you can expect builders to adjust their prices to buyers accordingly - while also adding other increased costs of materials and doing business.

If you're heading south and looking for a million-dollar home in Fort Lauderdale's Bay Colony area, call Merle Smith. His firm has completed a sprawling luxury dwelling with 265 feet of water frontage. The Fort Lauderdale News calls it one of the most expensive houses ever built on speculation - without a specific buyer in mind. And it's fully furnished.