It is the Monday question among people who collect this period, and the answer is usually a photograph followed by a second question: what is it? A lamp from a church rummage sale. A walnut table from the last hour of an estate sale. A piece of orange glass that might be Blenko and might not.

This is the collectors' corner of the site, and it works in both directions. Below is how to answer the question yourself: how to read a mark, how to find a real price, and how to work a sale. At the end is how to show us what you found.

Turn it over first

Before anything else, look underneath, inside the drawers and on the back. A surprising amount of midcentury furniture and glass says what it is, if you know how to read it.

Lane. The Virginia company stamped a serial number on its cedar chests and much of its furniture, and the number is the date of manufacture written backward. A piece marked 469280 reads as 08 29 64, or August 29, 1964. If there is a seventh digit, guides to the marks say it identifies the plant.

Blenko. The glassworks was founded in Milton, West Virginia, in 1921 and took the Blenko name in 1930. The trouble is that it rarely signed its work. WorthPoint's guide to the company estimates that only about one piece in ten carries a mark. From the 1930s to 1982 that mark was a silver foil sticker in the shape of a hand, which is easily lost. For a short period, 1958 to 1961, the name was sandblasted into the glass itself. Everything else is identified by shape and color against the work of its design directors: Winslow Anderson from 1948, Wayne Husted from 1952 and Joel Philip Myers from 1963.

Eames shell chairs. The official Eames site divides the fiberglass side chair into generations. The first ran from 1951 to 1959, and some of those shells carry a Zenith stamp. Patent labels appear from 1957. From 1959 to 1993 the Herman Miller name appears with a factory logo. Production then stopped for twenty years. Fiberglass shells made since 2013 have a new logo with Charles Eames's signature pressed into the shell, so a signature in the fiberglass means a new chair, not an old one.

Danish furniture. Pieces made in Denmark usually carry a maker's mark or a control stamp. One writer on the subject offers a blunt rule: if you find neither, the chances are that it was made in North America, where manufacturers licensed Danish designs in the 1950s.

When there is no mark

Most finds are unmarked, and then you are reading the object itself: the weight, the wood, the way the joints are cut, the hardware. That takes years of handling things.

For a head start, try our Photo Identifier. Give it a picture of a chair, a lamp or a house and it will read the style, the era and the likely designer, and show you the clues it used. Treat the result as a lead to follow up, not as an appraisal.

What is it worth?

An asking price is not a price. Anyone can list a lamp for $900. What matters is what one sold for.

The quickest free check is eBay. Search for the item, then turn on the filter called Sold Items. It shows roughly the last 90 days of actual sales with the price paid. The Completed Items filter adds the listings that ended without a buyer, which is a useful list of prices people refused.

Then be honest about condition, and remember that furniture is a local market. A credenza brings more in a city full of people looking for one than in a town where nobody is, and shipping it is expensive.

How to work an estate sale

An estate sale is run by a company that has priced the contents of a house and has a weekend, sometimes two, to sell them. Some sales simply open the door to the line. Others hand out numbers, as at a deli counter, so arrive early and ask.

The usual pattern, according to one industry guide, is full price on the first day, 25 percent off on the second and half price on the third, though each company sets its own schedule. That is the whole strategy. Go on the first morning for the piece you cannot bear to lose. Go on the last afternoon for a bargain.

Two points of manners. Do not carry around an armful of things you have no intention of buying. And put a sold tag on a large piece only if you mean it.

One caution about dishes

Old pottery can contain lead in the glaze or the decoration. The Food and Drug Administration's list of the pieces most likely to be a problem includes antiques, pieces that are damaged or heavily worn, and pieces brightly decorated in orange, red or yellow, which describes a good share of what turns up at a sale.

Home test kits are sold at hardware stores. If a piece tests positive, the agency advises strongly against using it to cook, serve or store food, and notes that no amount of washing will remove the lead. When in doubt, the casserole goes on a shelf and stays there.

Now show us

We want to see it. Upload a photo of what you found, tell us where you found it and what you paid, and we will run readers' pictures on the site with credit to you.

And if you found two of something, the second one can go in the Market.