"The price of the average share on the New York Stock Exchange relative to earnings is now lower than it was on the day after the October 1987 crash," observes Mutual Fund News Service (P.O. Box 937, Bodega Bay, Calif. 94923). "Share prices have risen since then. But earnings have grown even faster. So the average price-earnings ratio is actually lower than it was on Oct. 20, 1987. At the market peak the average P.E. was 60 percent higher than it is now."

- Speaking of low P.E. ratios, Sandor Cseh of Provident Capital Management in Philadelphia has earned 33 percent annually since 1985 on his managed portfolios by buying overseas stocks with low multiples. Cseh's disciplined approach leads him to sell whenever one of his company's valuations rises above the average for similar companies in its country. Cseh's cheapest favorites now: Banco Popular Espanol, Bank of Scotland, Bayer (chemicals, Germany), GAN (insurance, France), VNV (publishing, the Netherlands), Winsor Industrial (textiles, Hong Kong).- Even before Iraq invaded Kuwait, "the major oil companies were upping their capital spending budgets, particularly for overseas exploration and development," notes Standard & Poor's Outlook. "Since the Mideast is chronically unstable and U.S. production won't grow much soon, the majors will likely accelerate non-OPEC exploratory activity worldwide. Such activity will be great for oil service stocks for a long time to come." The Outlook's favorites: Halliburton, Parker Drilling, Schlumberger.

- Debt is out of fashion on Wall Street. But Forbes' Katarzyna Wandycz believes debt-bashing may have gone too far. She recently went looking for stocks that have been oversold in relation to their indebtedness. Her criteria: a debt-to-equity ratio over 80 percent, interest coverage over 2-to-1, debt less than 7 times cash flow, and minimum 12 percent 1990 projected earnings growth. Six candidates had single-digit P.E. ratios: Genlyte Group, Heekin Can, Leslie Fay, Loral, Scotsman Industries, Shaw Industries.

- After an exhaustive study of supply/demand fundamentals, Dan Rosenthal, editor of Silver & Gold Report (P.O. Box 510, Bethel, Conn. 06801) has finally turned bullish on platinum. Says Rosenthal, long a bear on the metal: "In the 1990s, the platinum market will be characterized by chronic shortages. Industrial consumption far outstrips mine supplies, and is growing twice as fast. You don't need a Ph.D. in mathematics to figure out the implications for platinum prices."

- "The coming bull market for grains will last longer, rise higher and be more volatile than any bull market witnessed since the mid-1970s, " says Commodity Insight (9369 Olive Street Road, St. Louis, Mo. 63132). "Grain prices will be led higher by the soybean complex. Sometime between now and the winter of 1991, soybean prices will rise $2 to $5 per bushel while corn and wheat rallies dramatically above the lows set in August."

- Last January the average one-country mutual fund sold for a 33 percent premium. Recently, they've been reduced to a 20 percent discount, as the international investing euphoria reversed field. "At this point," says closed-end-fund expert Thomas Herzfeld, "you don't have to differentiate too carefully." Still, Herzfeld does have favorite funds: Asia Pacific, Austria, Emerging Germany, First Philippine, France Growth, Italy, Japan OTC Equity.

Investor's Notebook reflects the opinions of professionals. It does not endorse specific investments, and no endorsement is implied or should be inferred. For more information, contact the individual firms cited.