The question I'm asked most about bats is, "How can you tell a 'real' bat from a store bat?" What I hope to do in this section is explain the traits of professional model bats and provide information that can help date those bats to particular eras. There are few concrete rules when it comes to authenticating and dating bats, but there are many well-researched guidelines that can help.

Much of the information on these manufacturers was drawn from three books: Louisville Slugger, A Complete Reference Guide by Malta; Bats, Professional Hillerich & Bradsby and Adirondack, 1950-1994 by Malta, Fox, Riddel and Specht; and MastroNet Reference and Price Guide for Collecting Game-Used Bats by Bushing and Knoll.

Hillerich & Bradsby (Louisville Slugger), 1897-1949

The labeling of Hillerich & Bradsby bats has changed many, many times since 1897. Still, there are a few key features that differentiate pro model game bats from store model bats.

In general, a pro bat must have "125" in the center label. If it has another number, such as "40 BR" or "125 LL," it almost certainly is a store bat. A pro bat also probably says, "Powerized" right of the oval; if it says "Flame Tempered," it's a store bat. If the knob has a number ("35" or "5") or a combination such as "RC 4" stamped into it, the bat is from the store. H&B stamped pro model numbers into the knob until 1976; after that, nothing would be stamped or branded into the knob until 2009. Professional ash bats have deep branding; store bats generally are foil stamped. Finally, pro bats have high-quality wood, while their retail counterparts often use inferior wood.

Once you have an idea whether your bat is a pro model or a store model, the next step is to identify the era the bat was used. Through the years, many collectors have researched bat markings and bat ordering records, trying to determine which markings were used in different years. While there typically is no perfect way to date a bat, there are general guidelines collectors can use.

Year	Comments	Illustration
1897-1911	The center label says: LOUISVILLE SLUGGER MADE BY J.F.HILLERICH & SON LOUISVILLE, KY.   The words, "TRADE MARK" may appear above or below the oval.
1911-1916	The words, "MADE BY" are replaced with a dash-dot-dash and "Co" is added after "SON." "TRADE MARK" is replaced by, "TRADE MARK REG. U. S. PAT. OFF."
1916-1917	"J.F.HILLERICH & SON Co" is changed to, "HILLERICH & BRADSBY Co."
1917-1921	The dash-dot-dash under "LOUISVILLE SLUGGER" is replaced with "125." The number 125 denotes a professional model bat to this day.
1921-1931	The dash-dot-dash under "HILLERICH & BRADSBY Co" is replaced with, "MADE IN U.S.A." Louisville Slugger, A Complete Reference Guide by Malta includes multiple variations during this period that may further refine a bat's era
1931	"Powerized" appears right of the center label. Underneath "Powerized" is "Pat. Pending."
1932	"Pat. Pending" is replaced with the phrase, "Bone Rubbed." Also, the word "GENUINE" first appears on the barrel above the player's name.
1933	"Bone Rubbed" is replaced with the phrase, "Oil Tempered."
1933-34	"Powerized" appears alone for the first time. If a bat has the 1921-31 center label and "Powerized" by itself, it must be from this era.
1934-44	"TRADE MARK REG. U. S. PAT. OFF." is replaced under the center label with the words, "TRADE MARK REG." The word "Powerized" has several different looks during this period (and through 1949). Generally, it will look more condensed than the version that begins in 1950 and the lightning bolts will be more pronounced or jagged.
1943-49	Model numbers are stamped into the knob of the bat beginning in 1943. By the end of 1944, all bats produced have the model number stamped into the knob. The model numbers are the only trait that differentiate this era from the 1934-44 era.