Edward (Nip) Wanzer, 57, once described as a kingpin of gambling rackets here was found shot to death last night in his Northwest Washington apartment.

Investigators said they believe Wanzer, with a record of more than 80 arrests but few convictions, was killed sometime Wednesday possibly during a robbery at his apartment at 1629 Columbia Rd. They said he had been shot once in the head.

Although Wanzer generally was able to avoid conviction on gambling charges, he was found guilty in 1975 of tax evasion after prosecutors contrasted his expensive life style with the relatively modest income he reported to the Internal Revenue Service.

Wanzer's tax forms had listed him simply as a small businessman, the owner of a haberdashery store on Georgia Avenue NW that helped provide him with a modest income, sometimes no more than $4,500 a year.

An investigation begun at the behest of the major crimes division of the U.S. attorney's office gave another picture of Nip Wanzer.

It showed a man who handled large sums of cash, wore costly clothing, paid $16,000 for a houseboat, and from 1967 to 1971 bought 12 cars, including five Lincolns and two Cadillacs.

After being convicted of underreporting his income over a four-year period by nearly $100,000, Wanzer was sentenced to serve up to five years in prison. It could not be determined last night how muich of the sentence he served.

Wanzer's body was found last night by his daughter, Pamela, who went to the apartment with the janitor of the building after she had tried unsuccessfully yesterday to telephone her father.

Although it was not clear whether anything was taken from the apartment, police said it appeared to have been "searched." There was no sign of forced entry, police said.

In suggesting robbery as a possible motive in the killing, investigators said Wanzer was known to have kept cash in the apartment.

Another theory advanced by police was that Wanzer may have been the victim of a gangland-style "rub out." They pointed out that Wanzer had made numerous enemies here.

Investigators said Wanzer was last seen about 2 p.m. Wednesday, the day on which they believe he was shot. The exact time of death could not be determined and an autopsy is scheduled.

Wanzer's tax evasion conviction came the year after a widely publicized trial in which he was acquitted of a charge that he had conspired to bribe policemen to provide protection for gambling operations.

After one of his numerous arrests on gambling charges, he pleaded guilty before U.S. District Court Judge Edward M. Curran in 1951 and was sentenced to a four-month to one-year term.

Wanzer was later permitted to with-draw the plea and went to trial before a jury. After being found guilty, he was sentenced to one to three years in prison by Judge Luther W. Youngdahl. That was apparently his most recent gambling conviction.

Where wiretaps and search warrants had failed to win convictions against Wanzer, the government's "net worth" examination, a sweeping inventory of his financial records and activities, succeeded in the 1975 tax trial.

IRS agents found in one 1975 investigation that in addition to a $62,000 house at 1400 North Gate Rd. NW, Wanzer had a luxury apartment in Prince George's County and s small farm in Accokeek, Md.

They produced records indicating that he deposited $19,000 in cash in a bank in a year when he reported amking less total income than that.

In Wanzer's defense, one of his lawyers said that his client dealt with large sums of cash because he could not read and therefore did not like dealing with checks and contracts.

"He conducts his entire life verbally," the lawyer said.

"I gambled, I played numbers, I did a little bit of everything," Wanzer said under crossexamination about his income.

Over the years he was described as a cook, as the owner of a delicatessen, as the operator of a lounge and a silent partner in liquor stores. Prosecutors called him a gambling "kingpin."

"I've been working and gambling all my life," Wanzer said at the tax trial.