A B737 CAPT ATTRIBUTED AN ALT BUST WHEN DEPARTING ZZZ TO THE COMPANY'S REQUIREMENT THAT CREWS FLY DIFFERENT SERIES OF THE SAME ACFT WHICH HAVE VARYING FLT DECK LAYOUTS.

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I WAS THE PF AND; TO BE HONEST; I CAN'T FIGURE OUT HOW THIS HAPPENED. WE WERE DEPARTING RWY WITH A R TURN TO 360 DEGS. AFTER BEGINNING THE TURN; CLEANING THE FLAPS UP AND ROLLING OUT TO A REVISED HDG; THE FO SAID 'ALT; ALT.' I HAD PASSED THROUGH 4000 FT (CLRNC LIMIT) AND WAS PASSING 4300 FT. I STOPPED THE ASCENT AT 4400 AND DSNDED BACK DOWN TO 4000 FT. CTLR SAID NOTHING. PERHAPS THERE WERE A FEW CONTRIBUTING FACTORS. OUR COMPANY OPERATES A FEW DIFFERENT VARIATIONS OF THE B737. DEPENDING ON THE SCHEDULE; ONE MAY NOT SEE (IN THIS CASE) A NEWER B737 FOR MONTHS. NEVERTHELESS; ANY GIVEN PAIRING MAY CONTAIN ALL OF THE DIFFERENT VARIATIONS ON ANY DAY. EACH HAS DIFFERENT CHARACTERISTICS; CONSIDERATIONS; EFIS/NON-EFIS AND DEGREES OF EFIS; PANELS AND SWITCHES IN DIFFERENT PLACES; ETC. I BRING THIS UP ONLY BECAUSE I REMEMBER WANTING TO TURN ON THE RADAR TO TAKE A LOOK AHEAD AND HAVING TO REACH IN DIFFERENT PLACES. I VAGUELY REMEMBER THE 'THOUSAND FT' CALL ('3000 FT 4000'); BUT THE RADAR; CLEAN-UP; AMENDED HDG AND PERFORMANCE OF THE ACFT MAY HAVE BEEN SUFFICIENT DISTRS TO BUST THE ALT. THIS WAS ALSO THE FIRST FLT WITH A NEW FO (DIFFERENT) AS HE HAD JUST JOINED US ON DAY #3 OF A 4 DAY PAIRING. I DON'T ADMIT TO LIKING THE POSSIBILITY OF FLYING DIFFERENT DERIVATIVES OF A MODEL; THE MOST RECENT OF WHICH WE; AS A GROUP; DON'T GET TO FLY OFTEN ENOUGH TO DEVELOP A 'FEEL' FOR THE ACFT. HAVING SAID THAT; I MUST ALSO SAY THERE WAS NO EXCUSE FOR THE BUST.