According to the project's change log, between 4.53 and 4.55 were performance improvements and bug fixes.
Index: Makefile =================================================================== RCS file: /cvs/ports/archivers/p7zip/Makefile,v retrieving revision 1.5 diff -u -r1.5 Makefile --- Makefile 15 Sep 2007 10:14:33 -0000 1.5 +++ Makefile 3 Dec 2007 22:47:36 -0000 @@ -5,7 +5,7 @@ COMMENT-main= file archiver with high compression ratio COMMENT-rar= rar modules for p7zip -V= 4.53 +V= 4.55 DISTNAME= p7zip_${V}_src_all PKGNAME= p7zip-${V} PKGNAME-main= p7zip-${V} Index: distinfo =================================================================== RCS file: /cvs/ports/archivers/p7zip/distinfo,v retrieving revision 1.4 diff -u -r1.4 distinfo --- distinfo 10 Sep 2007 10:52:40 -0000 1.4 +++ distinfo 3 Dec 2007 22:48:39 -0000 @@ -1,5 +1,5 @@ -MD5 (p7zip_4.53_src_all.tar.bz2) = MxRQRj1XN7upbL6iEVq+iw== -RMD160 (p7zip_4.53_src_all.tar.bz2) = IFuSDRQjgk5nW/qUKQwUEAJMN8o= -SHA1 (p7zip_4.53_src_all.tar.bz2) = V3YCXknRTzFI0qm109BnuxnG10U= -SHA256 (p7zip_4.53_src_all.tar.bz2) = Da9c6CDTocpZDrbu4mE3gVxryR2BPR0J/haLgvDdb10= -SIZE (p7zip_4.53_src_all.tar.bz2) = 1488885 +MD5 (p7zip_4.55_src_all.tar.bz2) = uxQVKc8jdKLhVzXxVScxcg== +RMD160 (p7zip_4.55_src_all.tar.bz2) = 0iRXJGHwS1OXbi5FptHDSqvaGNg= +SHA1 (p7zip_4.55_src_all.tar.bz2) = fdb3XAMfFfPTea8+II4uTWX1W7c= +SHA256 (p7zip_4.55_src_all.tar.bz2) = VgTCG0/sG3Pmv4tpsMP5ej8mnN2XXDvcXZYd5+2KCDU= +SIZE (p7zip_4.55_src_all.tar.bz2) = 1487801