BBM is not the only card manufacturer in Japan, nor is it the oldest. Calbee has been continually producing baseball cards since 1973.
Calbee cards come one to a pack. Each pack is attached to a bag of potato chips (occasionally over the years there have been Calbee cards with other snacks). I can not imagine actually attempting to collect these by pack! (I got a bunch of cards in 2002 and 2003 from a friend in Japan - he said he had to quit after that because his wife was tired of their living room being filled with potato chips.)
The first Calbee set was only around 90 cards. The next set (listed in Gary Engel's catalog as 1973-74) was 368 cards. Then the sets got big - the following years were 971, 1472, 933 and around 600. From the late 70's through the 80's, the sets varied in size from around 250 to around 750. From the 90's on, the sets tended to be in the 150-250 card range - although some of that depends on your definition of "set" as there are many subsets and what would be referred to as "insert" cards in other sets (can there be insert cards when there's only one card in the pack?)
Calbee card sizes have changed over the years. From 1973 to 1980, the cards were slightly smaller than US cards. From 1980 to 1990, they dropped to a smaller size. From 1990 until 1997, the cards were roughly the size of phone cards. From 1998 on, the cards have been roughly "standard" size (2 1/2 by 3 1/2 inches). (This excludes the occasional larger cards that were available by mail.)
For the most part, Calbee cards had no player names in English until 1989.
Most Calbee cards have featured a full bleed photo with minimal text on the front. Some exceptions to this are the 1975/76 "maroon bordered" subset (which kind of looks like the 1975 Topps set), the 1984 set and the 1990 "small" set. Up until 1990 cards would only have Japanese text on the front (if they had any). Starting with the 1990 "large" (phone-sized) cards (there were two different sizes in 1990), the names and later teams of the players would appear on the front in English. The card fronts seem to have pretty much standardized over the last 10 years to show the name (usually first initial and last name), team, team logo and uniform number.
Personally, I really love getting old (pre-1990) Calbee cards. The main and somewhat obvious reason is that if you want any cards from before BBM starting making them (1991), Calbee's your best option. They're also undeniably Japanese - there are no bones thrown to people like me who can't read the language. There's a lot of interesting little subsets (Nippon Series, monthly MVPs - the 1985 set featured a bunch of cards with portraits of the player drawn by fans) and the photography is extraordinary.
The more recent cards have interesting subsets as well - Best 9, All Stars, Sayanora Home Runs, Title Holders, etc. The 2001 set featured an 8 card subset for the 2000 Olympic team. The 2002 set celebrated the 30th year of Calbee cards with a subset featuring reprints of the rookie cards of a number of players. I'm guessing that Calbee puts more energy into the subsets because they'd be completely overshadowed by BBM otherwise, but I could be wrong.
The Calbee cards shown in the post are (from top to bottom), 1973 Kenichi Yazawa (#67), 1975/76 Toshiyuki Mimura (#333)from the "maroon bordered" subset, 1979 Mitsuyasu Hirano (unnumbered from the Nippon Series subset), 1984 Tatsunori Hara (#542), 1988 Bob Horner (#121), 1990 Choji Murata (#24 from the "small" set), 2002 Kosuke Fukudome (SH-6 from the Sayonora Home Run subset) and 2004 Atsuya Furuta (#59).
Sources for this post include Gary Engel's "Japanese Baseball Card Checklist And Price Guide" as well as Rob Fitt's Introduction To Japanese Baseball Cards. Thanks also to Jason Presley for the 1985 Calbee gallery.