The ex-date(the date on which the stock begins trading without its latest dividend) has occurred in late February since 1994. Specifically: Feb 25 in 1999; Feb 26 in 1998; Feb 27 in 1997; Feb 27 in 1996.
On each of those dates the stock opened at $2.00 a share below the closing price of the previous day. However, if you were to have looked at the price on the ex-date, it would be reported as unchanged from the day before, becasue the price-drop due to going ex-dividend is not a true price change. The change is not due to trading.
It is theoretically possible for the stock to regain the entire $2.00 a share during trading on the day it goes ex-dividend. In fact, that did not happen with NPK. However, in 1998, the price climbed from $39.00 to almost $43.00 in the first few days of March, after it had dropped on the ex-date.
You may be confusing the ex-date with the record date or the payment date. The ex-date is first, followed by the record date and then the payment date. NPK's payment date has occurred in March since 1994.
The stock has dropped considerably in recent months. Though I'm sure the price isn't headed for the low $20s, I cannot give you a rationale for buying it at this time if the plan is to scalp the dividend payment in hopes of a quick profit. In the current market environment, it is more likely that the stock will lose a little more ground after going ex-dividend because another year will have to pass before investors receive their next payment.
On the other hand, if management would return the shareholders' capital to the shareholders, all would be well. As I've stated before, either a large special dividend should be paid or the company should be sold. The two top dogs are not operating the company in the best interests of the majority of its shareholders.