diff --git a/src/mame/drivers/metlfrzr.cpp b/src/mame/drivers/metlfrzr.cpp
index 8846492bff3..83c4b40d579 100644
--- a/src/mame/drivers/metlfrzr.cpp
+++ b/src/mame/drivers/metlfrzr.cpp
@@ -1,5 +1,6 @@
 // license:BSD-3-Clause
 // copyright-holders:Angelo Salese
+// thanks-to: David Haywood, Peter Wilhelmsen
 /*************************************************************************************************************************
 
     Metal Freezer (c) 1989 Seibu
diff --git a/src/mame/machine/seibucop/seibucop.cpp b/src/mame/machine/seibucop/seibucop.cpp
index 99aabca96f1..b9ab6d11fff 100644
--- a/src/mame/machine/seibucop/seibucop.cpp
+++ b/src/mame/machine/seibucop/seibucop.cpp
@@ -3,6 +3,14 @@
 /***************************************************************************
 
  Seibu Cop (Co-Processor) device emulation
+  a.k.a. known as Toshiba gate array TC25SC rebadged as:
+  SEI300 - Legionnaire PCB
+  There's also a ROM labeled COP-Dx, which is probably used for some in-game maths: 
+  COP-D1 - Seibu Cup Soccer PCBs
+  COP-D2 - legionna.cpp and raiden2.cpp, latter might use another component too
+  COP-D3 - New Zero Team / Raiden 2 V33 HWs
+  Raiden 2 first boss arms is known to behave strangely without this ROM on a real PCB
+  
   (new implementation, based on Raiden 2 code)
   
  TODO:
diff --git a/src/mame/video/seibu_crtc.cpp b/src/mame/video/seibu_crtc.cpp
index 4d8c5a6bbe3..511f3046ebf 100644
--- a/src/mame/video/seibu_crtc.cpp
+++ b/src/mame/video/seibu_crtc.cpp
@@ -21,7 +21,8 @@ Raiden later rev (probably the first game to use it)
 
 TODO:
 - Most registers are still a mystery;
-- Get the proper Seibu chip ID number;
+- Get the proper Seibu chip ID number. 
+  Kold found that a Raiden alt set has irq request pin from a chip named SEI0160, which might be our man.
 
 preliminary memory map:
 (screen 0 -> Background)