Armour was also behind Stock & Share Trading Company, which had targeted shareholders of Tower, Vector, PGG Wrightson, Heartland and Rural Equities with low-ball offers before new regulations on the practice came into force last December.
These put stricter disclosure requirements on those making an offer and forced them to notify issuers of the approach.
Under the rules, shareholders also have up to 10 working days to cancel sales.
When announcing the changes last year, Commerce Minister Craig Foss said low-ball offers were a "predatory tactic" that damaged the health of capital markets.
Since the regulations came into play, Washington Securities has sent offers to Vector, Fletcher Building, Dorchester Pacific and Heartland shareholders.
Heartland group general counsel Michael Jonas said that while the rules had helped, he would like to see further changes made.
He said the regulatory notice now required to accompany low-ball offers could present key information more simply.
"In my view too many words lose people. I think what is fundamental is that the offer price is one thing and the current market price is another," Jonas said yesterday.
He also wanted offers to be required to reveal who the principals behind them were.
However, Shareholders Association chairman John Hawkins said the regulations already required the current share price to be put "right next door to the price being offered" and the total value of the offer.
"Frankly if people can't be prepared to read these things and consign them to the rubbish bin, then it's very hard to know what more you can do to help people. They do have to take some personal responsibility for their decisions," Hawkins said.
While the Financial Markets Authority had actively monitored unsolicited offers since the rules came to force, a spokesman said it was too early to tell what impact the offers were having on the market.
