for the products_prid in zencart database, table: orders field

[vivifashion]

for the products_prid in zencart database, table: orders field
the format is like '400:bc6a80a7a45bd92ce4978a362ab519ed'
does anyone know how this code generate?
the first is the products_id
then :
then bc6a80a7a45bd92ce4978a362ab519ed'
what is this code?

[vivifashion]

TABLE `orders_products`
============================================
orders_products_id => 3451
orders_id => 12994
products_id => 4421
products_model => '1-0101-90'
products_name => 'Black 828 Dynasty'
products_price => 0.0000
final_price => 82.6000
products_tax => 0.0000
products_quantity => 1
onetime_charges => 0.0000
products_priced_by_attribute => 1
product_is_free => 0
products_discount_type => 0
products_discount_type => 0
products_prid => '4421:d9456345cbaddd88adbe56fafea3bb68
--
orders_products_id => 3452
orders_id => 12994
products_id => 4442
products_model => '345'
products_name => 'Himalayan'
products_price => 0.0000
final_price => 166.6000
products_tax => 0.0000
products_quantity => 1
onetime_charges => 0.0000
products_priced_by_attribute => 1
product_is_free => 0
products_discount_type => 0
products_discount_type => 0
products_prid => '4442:24b8b49b38e2494500c018b913f1f841'
############################################
TABLE `orders_products_attributes`
============================================
orders_products_attributes_id => 3662
orders_id => 12994
products_options_values_id => 677
options_values_price => 118.0000
(other unnecessary data...)
--
orders_products_attributes_id => 3663
orders_id => 12994
products_options_values_id => 559
options_values_price => 238.0000
(other unnecessary data...)