There is a considerable amount of legitimate concern among serious sports card collectors about cards exhibiting signs of rebuilt corners. It's the attempt by a "card doctor" to add extra card stock to a corner that is worn or rounded from normal handling and age to dramatically increase the condition. It is safe to say that a rebuilding a corner and making it sharp can add great value to a card. Some are done well enough to get past the eye of even the most experienced professional grader and wind up being placed in a high grade holder.

Rebuilt corners are more than likely seen on vintage cards since they can carry a high value and are prone to corner wear. The process is especially dangerous because it is typically seen on rare and valuable cards and if done with skill, can be surprisingly difficult to detect, even by the best trained eye or card expert. It is also the alteration that is least likely to be detected by a collector because of the skill level required.

			Under ambient light and normal conditions, the corner of the above card looks very ordinary. It is nearly impossible to see the added card stock.

How corners are rebuilt:

A rounded corner has had some degree of paper loss; therefore to rebuild a corner this paper will need to be replaced. Typically there are three types of card doctoring methods used to accomplish this task but by no means is the list all-inclusive. These included corner replacement, inserting a plug or adding a home-made card stock. The idea seems preposterous but it's being done; perhaps not on a wide scale but evidence exists that it can not only be done, but done well enough to fool most everyone.

This is a magnified picture showing a corner from another card attached to a card which has had the original corner cut and then removed. It illustrates the start of a corner being rebuilt.

Sometimes an entire corner from another card is not used but instead a small solid piece of a similar card, referred to as a “plug” is inserted. A reverse tapered plug is then attached with an adhesive and ground card stock or fibers used as a filler.

This corner has been cut and has a tapered notch. It is ready to have a reverse tapered plug attached.

The final method does not incorporate the use of a solid piece but has a corner rebuilt using a home-made card stock. Traditionally this will be seen on a card that has a minor degree of corner wear that does not require a large area to be rebuilt. This new card stock mixture is molded to the card to create a sharp and distinct corner, with individually placed fibers used as for reinforcement. The image below shows home-made card stock added to the back of a card to rebuild a corner.

As talented as a card surgeon might be, it's possible to detect rebuilt corners. Regardless of the method used, the card examination for this alteration is the same. In addition to a halogen light and loupe, this inspection will require the use of a black light. If a rebuilt corner is not immediately noticeable the suspected corner will need to be studied very carefully and closely. As mentioned above, a corner that has been professionally rebuilt can be one of the most difficult alterations to identify. Also keep in mind more than one corner may be doctored in this way.

How to look for a rebuilt corner:

Under a halogen light, inspect the card corner and corner surfaces for inconsistencies in color, uneven wear, stray, unattached fibers as well as small high and/or low spots. Using your loupe, examine the suspected corner(s) and look very closely for individual fibers that may have been used as an attachment. These fibers will be close to the corner and may appear to be separated, crossed, stacked or spread apart further than normal.

A magnified view of what seems to be a professionally rebuilt corner. This is the same card displayed above where no abnormalities could be seen. Angled just right under a halogen light revealed the faint shadow of a slightly raised area. A closer examination showed that there was added stock to this valuable card. As you can see it slipped past the graders too!

Look for any discolorations or off colors that may be present. Often the adhesive used will not dry perfectly clear or may pick up a small amount of dirt when being mixed leaving a slightly darker corner tip. On the other hand it may be lighter in color because the replacement corner, plug, filler or adhesive could not be perfectly matched to the altered card.

Before and after with a stain added

Hold the card close to a black light and look for corners that have a slight illumination. Most of the card may seem to be dull or dark when compared to a light glowing corner. If used, more modern cardstock, starches, and some adhesives may not show under a halogen light but will be more noticeable when held by a black light.

		Although a bit fuzzy you can clearly see the brighter glow of the rebuilt card stock on each corner. Again, under normal light this is difficult to see.

Since the corner may have been molded into shape, inspect the end surfaces for possible areas where too much or not enough filler was used. If the adhesive did not work effectively or has become old and worn tiny fibers may stick out from the edges or corner surface. A less valuable vintage card can be ground up into powder and used as filler. The area serviced by filler may, however, have a different texture when compared to the rest of the card.

Home-made added stock using the powder from a card that's been ground up seems to be the most common type of filler used in rebuilding corners.

Check the corners and edges leading up to the corners for lack of a natural tone. Since new material has been added to the card, it will more than likely look newer that the rest of the card edges. Rebuilt corners will need to be shaped in one way or another. The edges leading up to the corner will need to blend evenly as the corner is shaped. This will certainly lead to a loss of the cards natural color tone since fresh cardboard is being exposed.

With this alteration is not unusual to see an edge with a nice even tone gradually get lighter as it gets closer to the rebuilt area. The card corner and edge may also show a darker than normal tone if the adhesive or mixture picked up any dirt or oils during the shaping or drying process.

A dark color can be normal, but in this instance, when examined under magnification, there are unnatural individual fibers placed to reinforce the corner. A closer study of the corner and edges showed this to be added stock which was discolored. The value of this particular card had its value increased by several thousand dollars based on the improved condition. It, too, was graded.

Rebuilt corners do not always have that professional look. Added stock will, at times, can be somewhat obvious when magnified. Granted the area will still need to be closely examined so it is not mistaken for paper loss or areas of wear. A less than professional job may look like a small (tiny) wad or the high and low spots may be more prevalent.

	Here we have two different vintage cards from the same collection. Each has a rebuilt corner which was presumably done to hide or cover a trim job gone bad. At first glance the card to the right looked like the corner had a small inward fold. Each of these have been appropriately graded as "authentic" meaning the alteration(s) were detected. Also, don't think that because a card came from a noted collector it is not altered. These two cards are from the famed Lionel Carter collection.